What is the difference between OptaPDF and CustomizedPDF?

OptaPDF processes files on a secure server, which lets it run heavy tasks like Office-to-PDF conversion and OCR. CustomizedPDF runs entirely in your browser, so your files never leave your device — ideal for maximum privacy on simpler operations like merging, splitting, and rotating.

Are in-browser PDF tools more private?

For supported tasks, yes — if processing happens entirely in your browser, the file is never uploaded anywhere, which is the strongest possible privacy. The trade-off is that browsers cannot run heavy engines like LibreOffice or OCR, so complex conversions still need a server-side tool such as OptaPDF.

Which should I use for OCR or Word-to-PDF conversion?

Use OptaPDF. OCR and Office document conversion require server-side engines (Tesseract, LibreOffice) that browser-only tools cannot run. For simple, fully local edits, CustomizedPDF is a great privacy-first choice.

Yes, both OptaPDF and CustomizedPDF are free to use with no watermarks.

PDF Comparisons

OptaPDF vs CustomizedPDF: Server-Side vs In-Browser PDF Tools (2026)

By The OptaPDF Team • Published June 24, 2026 • 7 min read

Not all "online PDF tools" work the same way under the hood, and the difference matters for both privacy and capability. OptaPDF is server-side; its sister site CustomizedPDF is fully in-browser. Neither is universally "better" — they are built for different jobs.

How they differ technically

	OptaPDF (server-side)	CustomizedPDF (in-browser)
Where files are processed	On a secure server, then auto-deleted	Entirely on your device
Are files uploaded?	Yes (encrypted, deleted in 30 min)	No — they never leave your browser
Heavy tasks (OCR, Office conversion)	Supported	Not possible in-browser
Simple tasks (merge, split, rotate)	Supported	Supported, instantly and offline
Works offline	No (needs the server)	Yes, once the page is loaded

When to use CustomizedPDF (in-browser)

If your task is simple and your document is sensitive, in-browser processing is the gold standard for privacy because nothing is uploaded at all. Reach for CustomizedPDF when you want to merge, split, rotate, or reorder pages of a confidential file and you would rather it never touch a server.

When to use OptaPDF (server-side)

Some jobs simply cannot run inside a browser. Converting a Word, Excel, or PowerPoint file to PDF needs a full office engine; OCR needs a recognition engine; high-fidelity PDF-to-Excel extraction needs server-side parsing. For these, OptaPDF does the heavy lifting and then permanently deletes your file within 30 minutes. Use OptaPDF for:

Word/Excel/PowerPoint to PDF and the reverse.
OCR on scanned documents to make them searchable.
Heavier compression and format conversions.

The best workflow: use both

Because they are part of the same network, you can mix them. Do the privacy-sensitive, simple steps in-browser with CustomizedPDF, and bring the heavy conversion or OCR steps to OptaPDF. You get maximum privacy where it is possible and full capability where it is needed.

Quick decision guide

Confidential file + simple edit? CustomizedPDF (stays on your device).
OCR, Office conversion, or heavy processing? OptaPDF (server-side power, auto-deleted).
Not sure? Start with OptaPDF — it covers the widest range of tasks.