Okinawa Software Lab

Your PDFs never leave your PC.

We make small PDF tools — and a free file checker — for Windows, from Okinawa, Japan. Sort and print, mark up and redact, check before you send, know what a file is before you open it. Nothing you open is ever uploaded. All four are on the Microsoft Store.

Fully offline Originals untouched One-time purchase

Apps

Four tools, four jobs

Rather than one app that tries to do everything, each tool takes one problem and makes it something anyone can handle.

PDF Sort & Print

Stop opening files one at a time just to print them.

Drop in PDFs and images (JPG/PNG), whole folders too, then put them in order and print the set in one pass.
Sort by date added, date modified, document date, natural filename order, or by hand. One click reverses any of them.
Document date reads each photo's capture time and each PDF's creation date, so copying files never scrambles the order.
Print directly and no combined file is left behind — nothing to clean up when the documents hold personal data.
300 files in a few seconds. Hundreds of files sort instantly.

Price: Free — every feature, today

A future version may turn batches of more than 10 files into a paid option. Up to 10 files will stay free.

Get it on Microsoft Store No sign-up. Free, as it is.

PDF Markup & Redact

Mark it up. Black it out. Print it.

Fix existing text: click any text and retype it, like correction tape on paper. Font, size and colour match automatically.
Highlighter, underline, boxes, text, shapes and speech balloons, plus fourteen stamps, a date stamp and your own stamp images.
Redaction is free: black-out, white-out or mosaic. Pages are saved as images, so the text underneath cannot come back.
Scanned documents too: a click selects the text automatically (recognition runs on your PC only).
Rotate, crop, delete pages, start from a blank sheet, and poster printing across several sheets. SVG images open too.

Free: Everything except saving and printing — redaction included
Pro: One-time purchase — save as PDF, save as JPG, print, split printing

The price for your country is shown on the Microsoft Store. There is no subscription.

Get it on Microsoft Store No sign-up. Start with the free version — mark up and redact right away.

PDF Privacy Checker

Are you certain that redaction removed anything?

A black box drawn over a name often hides it only from your eyes — copy-paste and AI tools can still read what is underneath.
In PDFs: same-colour, transparent, covered, off-page and tiny text, annotations, form fields, metadata, and text left in earlier revisions.
In photos: GPS location, capture time, camera model, author name, and the pre-edit thumbnail.
Editing history and signs of AI generation are read out, never asserted — the records that exist, listed as they are. Your original is never altered; removal always makes a copy.
Reports carry the full body text as an appendix, with every hidden passage marked in colour where it sat.

Free: Every check, and everything it found — you can see what is inside without paying
Pro: One-time purchase — save reports, create a cleaned copy, X-ray view, GPS coordinates and map, history analysis

The price for your country is shown on the Microsoft Store. There is no subscription.

Get it on Microsoft Store No sign-up. Every check runs to the end in the free version.

File Type & Safety Checker

Know what a file really is before you open it.

“Is this attachment safe to open?” — answered in plain words. Just drag and drop. Works on files that won't open or show a blank icon.
About 180 extensions recognised. About 70 formats are verified from the file's own signature, and a file with no extension is identified from its contents.
Warns about double extensions (“invoice.pdf.exe”), executables posing as documents, macro-enabled Office files, and shortcuts (.lnk) that hide their target. New
Executables get a digital signature check with the publisher's name. Downloaded files show where they came from.
Check a whole folder at once; results come most-dangerous first in one printable report. Read-only and fully offline. Not a replacement for antivirus.

Free: Everything is free — the check itself will always be free

Get it on Microsoft Store No sign-up. Free, and staying free.

Articles

Write-ups on how the apps work under the hood, published on DEV Community. Per-app release notes live on each app’s Microsoft Store page.

2026-09-23 pdfium and pypdf return different text from the same PDF — four mismatches to know before you feed PDFs to an LLM — The same PDF yields different text depending on which library reads it. Four mismatches we hit while checking for hidden text, with a script that reproduces each one.
2026-09-17 Catching “invoice.pdf.exe” before you open it: a tool that identifies a file’s real type from its first bytes — Signature matching, double extensions, macro detection and Authenticode checks: how File Type & Safety Checker decides, what it got wrong on real files, and where it stops.
2026-09-16 I built a tool that finds “invisible text” hidden in PDFs — white text, tiny fonts, and the invisible render mode. How PDF Privacy Checker decides what is hidden: the thresholds, why they are what they are, and the fight against false positives.

All articles on DEV →

Principles

The same three promises, in every app

Fully offline

Nothing you open is sent over the internet — not a page, not a thumbnail. Every operation finishes on your own machine. The only time an app talks to a server is when the Microsoft Store handles a purchase or confirms that you own Pro.

We never touch the original

Your file is never silently rewritten or deleted. When something has to be removed, a separate copy is created. Evidence, deliverables and records cannot be destroyed by a mis-click.

Bought once, yours

Every paid version is a one-time purchase. No subscriptions. The purchase lives on your Microsoft account, so a new PC or a clean reinstall never means paying again.

FAQ

Questions we get

Is any part of my document uploaded?

No. These are desktop applications, not web services. The contents of the files you open never leave your computer — you can disconnect from the network entirely and every feature still works. The one exception is the Microsoft Store purchase flow, which handles payment and licence checks and never sees your documents.

Do I need to create an account?

No. There is no sign-up, no login and no telemetry. If you buy a Pro version, that purchase is recorded against the Microsoft account you already use for the Store — the same as any other Store app.

Will Windows warn me when I install?

No. All four are distributed through the Microsoft Store and reach you signed by Microsoft, so you will not see the blue warning screen that appears when running a downloaded .exe.

Is there a Mac or mobile version?

Not at the moment. Windows 10 and 11 only.

Will PDF Privacy Checker find every possible way of hiding something?

No, and we would rather say so plainly. It detects the common techniques, but file formats are endlessly varied and no tool can promise to catch everything. Text that has been baked into an image — a photograph of writing — is outside its scope. Treat it as a strong last check before you send, not as a guarantee.

Who makes these?

Okinawa Software Lab, a small independent developer in Okinawa, Japan. The tools grew out of everyday office work: too many files to print one by one, and documents that had to be checked before they went out of the building.

Contact

Get in touch

Bug reports, questions and "I wish it could do this" are all welcome by email or through the form below. Requests genuinely shape what gets built next. The same form opens from the Contact button inside each app.

Email — info@okinawasoftwarelab.com English form