Most "free" PDF tools aren't. You find that out at the worst moment — you've already uploaded the file, waited for it to process, and then a paywall screen appears. I've been annoyed by this enough times that I spent a Saturday testing a bunch of them on the same set of tasks.
Here's what I found.
What I tested
Four tasks, same file each time: compress a 15MB presentation, merge three PDFs, extract two specific pages, and convert a scanned PDF to Word. I noted exactly where each tool stopped me and what it wanted from me before letting me continue.
PDFSass
This one surprised me. pdfsass.com has 35-odd tools, which usually means you're in for a "free for the first one, pay for the rest" situation. But I ran it with network monitoring open and the file processing is genuinely happening in-browser via WebAssembly — nothing gets uploaded to a server. My 15MB test file compressed to about 3MB without visible quality loss.
I didn't hit a single limit during testing. No account prompt, no watermark on output.
The interface is utilitarian. That's honestly fine.
iLovePDF
Reliable and fast. Has been around for years and handles batch operations well. The free tier has file size caps and a few tools push you toward sign-in, but for typical single-file jobs it works without friction.
Smallpdf
The best-designed tool in this list by a significant margin. Clean, fast, well thought out.
And then it tells you to wait an hour after your second task. The free tier is 2 tasks per hour, and after a few sessions it asks you to create an account. That's a legitimate business model — they need to charge for something — but calling it a "free PDF tool" is a stretch. More accurate: free tier with limits that kick in faster than you'd expect.
PDF24
Open source, no limits on the free tier, about 45 tools. The interface has the energy of something designed in 2011 and maintained consistently but without much new investment in design. I mean that as a neutral observation — it works, nothing is hidden behind a paywall, and it handles batch processing well.
If you process PDFs often and aesthetics aren't a priority, this is probably your answer.
Sejda
Worth calling out specifically: Sejda is the only tool in this list that lets you edit text directly inside a PDF, rather than converting it to Word first and back. That's actually a harder problem than it sounds, and most tools skip it. Sejda does it reasonably well.
Free tier caps at 3 tasks per hour and 200 pages or 50MB per file. Enough for most editing jobs.
Adobe Acrobat Online
Only covers a few things for free — compress, convert, sign. But it does those things really well, which makes sense given that Adobe created the format. If you're converting one document and accuracy matters more than speed, this is the right tool.
Not the right call for batch work or anything outside those three functions.
CleverPDF
Supports 44 format conversions. That's the whole pitch. If you need to convert a PDF to EPUB, DjVu, or something equally obscure, this is the only free option I found that handles it. No account, no limits on basic conversions.
So what's actually free?
PDFSass and PDF24 are the only two where "unlimited free" actually held up across all four tasks. The others either have hourly limits (Smallpdf, Sejda) or file size caps (iLovePDF) or are just limited in scope (Adobe).
For editing text inside a PDF without converting to Word: Sejda.
For obscure format conversions: CleverPDF.
For a polished UI with occasional use: Smallpdf, with the expectation that you'll hit limits.
The tools I kept: PDFSass when I don't want files leaving my browser, PDF24 for anything batch-related.