BoltPDF

What changed in 0.11.6 · 7 October 2026

Fixed clipped text in text boxes — enlarge the text in a text box (annotation) and the box grows with it; add lines and the box extends downward so every character shows (before, going past about 24pt clipped the overflow outside the box)
Improved box fits the text exactly — when you write with Add Text, the box hugs the text size and grows as you type or enlarge it. There's no empty gap beside it, so you can click right next to it to add more text
Added move and resize the text box — drag the round handle at the top-left to reposition before committing (reopened text too), and a text box can be resized by dragging its bottom-right corner even while typing. The text's baseline stays put when you resize, so it lands exactly where the preview showed

Run the installer over your existing version and it updates in place. What follows still describes the large changes made in 0.11.1; earlier changes are in the version history below.

Aiming to be the free PDF editor
that handles Korean documents best.

BoltPDF is a Windows PDF editor that covers viewing, editing, signing and converting in one program. It reads scanned Korean with very few mistakes, edits text inside a photo while matching the colour, weight and background, and adds up the totals in a form PDF for you. Completely free — no ads, no sign-in, no tracking.

3.5x

Opening a document
vs the previous engine

49ms

2,000-page PDF
time taken to open it

40%

less memory
vs the previous engine

4 languages

Korean first
English, Japanese, Chinese

0 cost

Ads, sign-in, tracking
none of them

BoltPDF start screen with recent files and quick actions — **Start screen** — recent files and the jobs you do most, right as it opens. Dropping a file onto it works too.

The PDF engine is now our own

From 0.10.0 the PDF engine changed from the widely used open-source MuPDF to YsPDF, written from scratch in Rust. These are three alternating runs on the same PC with the same 2,000-page PDF, against 0.9.3 which used MuPDF.

Measurement	0.9.3 MuPDF	0.11 YsPDF	Difference
Open the document	172–186 ms	49–51 ms	about 3.5x
First page painted	40–49 ms	19–22 ms	about 2x
Jump to page 1,000 and paint	14–32 ms	13–15 ms	faster and steadier
Search the whole file (first run)	476–480 ms	117–202 ms	about 2.5–4x
CPU for one second of smooth scrolling	500–1,187 ms	390–640 ms	less CPU
Memory after the test	709–834 MB	463–475 MB	about 40% less

Measuring the engine alone says the same Rendering all 103 real-world PDFs took 19.95s → 3.84s (about 5x); text extraction 10.95s → 2.66s (about 4x); a large JPEG 2000 image 1.57s → 0.13s (about 12x). Not one of the 103 files got slower, and all 30 benchmark items were faster than before or the same. Files over 1GB open straight away.

※ The comparison is against BoltPDF 0.9.3, which used the MuPDF engine. These are not figures against another company's product; they were measured alternately with the same files on the development PC (AMD Ryzen 9 3900X).

BoltPDF document view showing a contract PDF — **Document view** — page turns and zooming never stutter

BoltPDF dark mode — **Dark mode** — for long documents at night

Strong with Korean

This is where most of the work went in 0.11.1. Korean in a scan or a photo is read first with the Korean recogniser built into Windows 10 and 11. Area text recognition and "make a searchable PDF" both use it; on a PC without the Korean recogniser it falls back to the built-in engine (Tesseract) as before.

BoltPDF Korean OCR result reading a menu board photo correctly — **Korean OCR** — it reads "Today's menu / Americano 3,900 won / Caffè latte 5,000 won / Cheesecake 6,500 won" from the menu photo exactly. These are the words the previous engine used to get wrong.

It also has the things people in Korea actually need: seal across page edges (ganin), stamping every page, and making Korean-style signatures and seals; Hangul (HWP) → PDF conversion; automatic redaction of personal data such as resident registration, account and phone numbers; and Korean formats such as ₩ and "yyyy년 m월 d일".

BoltPDF automatic redaction of personal data — **Redaction** — found and permanently removed

BoltPDF stamping every page — **Stamp every page** — including the seal across page edges

BoltPDF signature and Korean seal creation — **Signatures and seals** — build round or square seals yourself

BoltPDF editing PDF text directly — **Editing text directly** — keeping the original font, size and colour

Editing text inside a photo

For when the prices on a menu board changed but the original file is long gone, or a single character in a scanned document is wrong. 0.11.1 brings this up to the level of paid software.

It lifts the colours for you

The eyedropper picks the original text and background colour straight off the document, and there is a colour panel, #RRGGBB input, recent colours and a reset to the original.

It blends into the photo

Match the weight (hairline to very bold), opacity, blur, letter spacing and glyph width so the new text looks like it was always part of the picture.

It fills in what you erased

"Match the surroundings" fills the erased area from the patterns and gradients around it, so there is no obvious rectangle left behind.

BoltPDF editing text in a menu photo — changing a price — **Mid-edit** — changing a price on a photo of a menu

BoltPDF result after editing text in a photo — **The result** — it looks like it was there all along

BoltPDF image text editor with weight slider, eyedropper, fill style and fine-tuning — **Reopen and edit again** — double-click text you already edited and it opens with the same text and styling

BoltPDF text colour panel with saturation, hue bar, eyedropper and recent colours — **Colour panel** — the eyedropper picks a colour straight from the document

New text is dragged with the mouse (hold Shift to keep it on one axis) and nudged a step at a time with Alt and the arrow keys. Even after applying, hovering over it offers "double-click to edit or move", and double-clicking reopens it, replacing the earlier edit cleanly.

Form PDFs and print work

In a PDF with fields — a quotation, an application form — type in a quantity and the total updates by itself. Calculations built in another PDF program (sum, average, product, max, min) work as they are, alongside number, currency (₩), percentage, date, time and phone formats, and input range checks. Enter something that does not fit and it tells you in Korean, like "The 'Quantity' field only accepts values between 1 and 99.".

BoltPDF detecting form fields on an event application form — **Field detection** — it finds the input boxes on a paper form and suggests them

BoltPDF field properties dialog with name, tooltip, required and maximum length — **Field properties** — required flag, character limits and more

Before sending anything to a print shop, print preview (overprint) shows on screen how the overprint settings will actually come out (View tab; only the display changes, the file does not). In 0.11.1 the print colour (CMYK) display was rebuilt on the international print standard (ISO 12647-2), so what you see is closer to the printed result. There is also print-ready PDF (outlined text), PDF/A archival export, and PDF inspection and repair.

BoltPDF PDF/A-2b archival copy saved — **PDF/A archival export** — in the long-term preservation format

BoltPDF inspecting and repairing a damaged PDF — **Inspect and repair** — it repairs a broken file as it reads it

Finding, marking and working together

Regular-expression search means a pattern like \d+(\.\d+)?% finds every percentage in a contract at once, with the surrounding context shown for each hit. You can also search every open document at once.

BoltPDF regex search with case, word and regex options and context previews — **Regex search** — context shown with every hit

BoltPDF searching across all open documents — **Search all documents** — results grouped by document

BoltPDF annotations — highlighter, underline, note, shapes, text box — **Annotations** — highlighter, underline, notes, shapes, text boxes

BoltPDF note replies with an accepted status — **Note replies** — filter by author, type or status

BoltPDF rich text box with a formatting panel — **Rich text box** — text colour, background and border

BoltPDF measuring area and perimeter on a floor plan with a cloud border — **Measuring** — set a scale and measure area, perimeter and length

Page work and conversion

0.11.1 makes working in the thumbnail pane easier. Shift-click for a range, Ctrl-click one by one, then delete, rotate or extract them all at once; Delete and Ctrl+A work too. A document scanned two pages to a sheet is split with split in half (left/right or top/bottom, with "right first" for books read right to left).

BoltPDF multi-page selection — 2 pages selected — **Multi-page selection** — pick them, handle them in one go

BoltPDF page editing view — **Page editing** — reorder, rotate, extract

BoltPDF convert menu — Word, Excel, PowerPoint, images — **Convert** — to Word, Excel, PowerPoint or images

BoltPDF tools menu — **Tools** — merge, split, compress, batch

BoltPDF bookmarks styled with colour and bold, reordered by dragging — **Bookmarks** — colour and bold, reordered by dragging

BoltPDF page label settings — **Page labels** — "Summary" at the front, then 1, 2, 3…

From this version, PDFs show their first page as a thumbnail in File Explorer. Turn it on during installation (or in settings for the portable build) and off again whenever; a damaged file in the folder will not hang Explorer. And if it closes unexpectedly, what it saved automatically is restored the next time you start it.

BoltPDF crash recovery dialog listing auto-saved documents — **Recovery** — reopen after a crash and the documents you were working on come back.

An AI assistant (optional)

Everything works with AI switched off. Only if you want it, add your own API key or connect an AI on your own PC (Ollama, LM Studio). Then it summarises, translates and answers questions — and carries out document tasks too, such as "add a summary page at the front". Each task is shown as a card first, and can be undone after it is applied. Personal data is redacted before anything is sent.

BoltPDF AI summary — demonstration screen — **Summary** — for skimming a long contract first

BoltPDF AI task card — demonstration screen — **Task card** — it shows what it will do before doing it

BoltPDF AI task applied — demonstration screen — **The result** — a summary page went in at the front

BoltPDF AI settings with service, model and API key — **AI settings** — a cloud service, or an AI on your own PC

The AI screens above are demonstrations They were captured with prepared answers rather than a live AI service. To use the AI features you have to add your own API key or connect an AI on your own PC. The names, company names, amounts and contact details on screen — and the menu, floor plan and application form — are all made-up demonstration material.

Four languages, and quick control

Korean comes first, with English, Japanese and Simplified Chinese interfaces. The command palette (Ctrl+K) finds features from Korean initial consonants too — type "ㅎㅊ" and "Merge" comes up.

BoltPDF command palette finding Merge from Korean initial consonants — **Command palette** — Ctrl+K, initial-consonant search

BoltPDF explaining a selected passage — demonstration screen — **Explain simply** — select a difficult clause and ask (demonstration screen)

BoltPDF AI highlighting and annotating — demonstration screen — **Hand over the marking too** — "highlight the risky clauses" is a job you can delegate (demonstration screen).

Installing, and what you need

Operating system	Windows 10 (1809 or later) · Windows 11, 64-bit
To install separately	Nothing. The runtime it needs is included
Installer	`BoltPDF-0.11.6-Setup.exe` — no administrator rights needed. During installation you can choose "open PDFs with BoltPDF" and "PDF thumbnails in Explorer"
Portable	Unzip and run `BoltPDF.exe`. Explorer thumbnails are enabled in settings
Price	Free · no ads · no sign-in · no tracking

The "Windows protected your PC" dialog on first run It appears because no code-signing certificate is used. Click "More info" → "Run anyway" to continue. You can check the file against the SHA-256 values below first.

# PowerShell
Get-FileHash .\BoltPDF-0.11.6-Setup.exe -Algorithm SHA256
Get-FileHash .\BoltPDF-0.11.6-portable.zip -Algorithm SHA256

# Expected values (0.11.6)
# BoltPDF-0.11.6-Setup.exe
# 386c339449292d79491e60ab0eb107de1078368ff6fa0d6e52cbd7e06057bade
#
# BoltPDF-0.11.6-portable.zip
# a3ce96c8ade926e29153afb8126504f7fae5101cebe8a9082a52f6630350bca4
#
# BoltPDF.exe inside the archive
# 0317c298113ecf3e17141123d7755e883027adca3f34f8c1595269bf133dc92c

Licence

Free software (freeware)

· Free for anyone — individuals, companies, schools and public bodies alike, with no limit on machines or time.
· Redistribute it freely, exactly as you received it (a website, a download archive, internal distribution, a USB stick). Just do not alter the files inside or bundle anything with it, and pass the licence files along with it.
· It may not be modified or sold. Decompilation and reverse engineering are not permitted, nor is selling it, and the source code is not published.
· The open-source components inside (Qt, Tesseract OCR, the Pretendard typeface and others) follow their own licences. Qt is linked dynamically under LGPL-3.0, so it can be swapped for another build of the same Qt version.

Full text: Licence agreement (LICENSE.txt) · Copyright and third-party component licences

※ Up to 0.9.x this was released as AGPL-3.0 open source. When the PDF engine was replaced with our own YsPDF in 0.10.0, the licence changed to free closed-source software (freeware). Using and redistributing it stay as free as before, but the source code is no longer published.

Frequently asked questions

Is BoltPDF really free?

Yes. There is no advertising, no sign-in, no paid tier and no time limit. It is free for business use in companies, schools and public bodies as well as for individuals, with no limit on the number of installations.

How much faster is it than the previous version?

From 0.10.0 the PDF engine was replaced with YsPDF, written in-house. Measured on the same PC with the same 2,000-page PDF against 0.9.3, which used MuPDF, opening a document is about 3.5x faster (172–186ms → 49–51ms), a whole-file search about 2.5–4x faster, and it uses about 40% less memory. These are figures against the earlier version, not against another company's product.

Does it recognise scanned Korean properly?

From 0.11.1 it uses the Korean recogniser built into Windows 10 and 11 first. A Korean Windows installation already includes it, so there is nothing to install, and both area text recognition and "make a searchable PDF" use it. On a PC without it, the built-in engine (Tesseract) is used instead.

Does edited text in a photo look obvious?

The eyedropper lifts the original text and background colour, and you can match the weight, opacity, blur, letter spacing and glyph width. The erased area is filled from the surrounding pattern with "match the surroundings", so little of a rectangle is left. Even after applying, a double-click reopens it to edit or move.

Will totals calculate themselves in a quotation PDF?

Yes. Sum, average, product, max and min calculations are supported, along with number, currency (₩), percentage, date, time and phone formats and input range checks. Calculations built in another PDF program work as they are.

Where can I get the source code?

From 0.10.0 the source code is not published. Up to 0.9.x it was AGPL-3.0 open source, but building our own PDF engine came with a change to free closed-source software (freeware). Using it and redistributing it exactly as received are still free.

Can we share it around a company or a school?

Yes. As long as it is exactly as you received it, internal distribution, posting it in a download archive and handing it out on a USB stick are all fine. Just do not alter the files inside or bundle anything with it, and include the licence files (LICENSE.txt and the copyright and licences file). Selling the program itself is not allowed.

Do I have to use the AI features?

No. Everything works with AI switched off. Turn it on only if you want it, with your own API key or an AI on your own PC such as Ollama or LM Studio, and personal data is redacted before anything is sent.

A warning appears when I install it.

That is the "Windows protected your PC" notice, which appears because no code-signing certificate is used. Click "More info" → "Run anyway" and the installation continues. If you would rather be sure, check the SHA-256 values above against the file you downloaded.