Need a reliable free PDF signing tool recommendation

General
1

I need a trustworthy, free PDF signing tool for work documents and contracts that lets me add secure digital signatures without watermarks or hidden limits. I’ve tried a couple of online options, but they either cap the number of documents, downgrade quality, or require a paid upgrade to actually save the signed file. What free tools are you using that are safe, truly free, and work well on both Windows and in a browser?

2

Short answer for work-grade PDF signing without watermarks or sneaky limits:

  1. Adobe Acrobat Reader DC (free version)

    • Works on Windows and macOS.
    • Use “Fill & Sign” for simple signatures.
    • Use “Certificates” tool to add a real digital signature with your own cert.
    • No watermark, no page limits.
    • Downsides: interface is a bit bloated, but it works for contracts and HR docs.

  2. Foxit PDF Reader (free)

    • Also supports digital signatures with certificates.
    • Lighter than Adobe on a lot of machines.
    • No watermark on signed PDFs.
    • Good for filling and signing standard forms.

  3. LibreOffice + PDF

    • Open the PDF in LibreOffice Draw.
    • Sign using a certificate via “Digital Signatures”.
    • Export back to PDF.
    • Good if you use Linux or want open source.
    • Not perfect for complex PDFs, but fine for contracts and simple layouts.

  4. qpdf + command line (if you like nerd stuff)

    • For Linux and advanced users.
    • Lets you sign PDFs with a certificate in a scriptable way.
    • Good for batches of documents.
    • Not friendly if you hate terminals.

For legal and secure digital signatures, use a proper certificate based signature, not only drawn signatures. A drawn or typed signature works for informal stuff, but for higher compliance standards you want a certificate bound to your identity.

Quick setup tip:

  • Get a personal signing certificate from a trusted CA (some workplaces provide one, some countries issue ID certs).
  • Import it into your OS keystore or Adobe’s certificate store.
  • Use Adobe or Foxit “Certificates” feature, not only “Fill & Sign”.

If you want no uploads at all, avoid web tools like Smallpdf, PDFfiller, etc. They often have caps or hidden paywalls, and your docs sit on their servers.

For most office needs, Adobe Reader free version plus a proper certificate covers everything without watermarks or weird limits.

3

If the online tools annoyed you, you’re not alone. The “free*” with tiny asterisk trend is brutal.

Since @voyageurdubois already covered Adobe / Foxit / LibreOffice pretty well, here are some different options that stay local, are actually free, and don’t slap watermarks on your stuff:

  1. Okular (Linux, Windows)

    • KDE’s PDF viewer.
    • Supports digital signatures with certificates.
    • No watermarks, no hidden limits, totally local.
    • UI is a bit old-school, but it’s stable and not bloated.
    • Great if you’re in a Linux-heavy or mixed OS environment.

  2. Xournal++ (Linux, Windows, macOS)

    • More for handwritten signatures, but handy for contracts where a drawn or image signature is legally fine.
    • You can annotate and “sign” on top of PDFs, then export as PDF again.
    • Not a full-blown certificate-based sign tool, so I’d use it for lower-stakes docs, not strict compliance workflows.

  3. PDF-XChange Editor (free tier)

    • Careful here: it can watermark some editing features, but simple signing with an existing signature appears without watermark if you do not use the “premium” tools.
    • Lets you create a signature appearance and stamp it where needed.
    • Interface is cluttered, but once you learn which tools not to touch, it’s usable without random logos all over your contracts.

  4. Digidoc-style tools (country specific)

    • If you’re in an EU country or somewhere with national eID, check if your gov or ID provider ships a desktop signing app.
    • Example: many eID ecosystems have a signing client that creates proper PAdES compliant PDF signatures using your national ID or smart card.
    • These are typically free, strongly compliant, and 100% local. Downside: setup can be painful, smart card readers, drivers, etc. But for serious contracts this is actually the “grown up” solution.

  5. Thunderbird + external signing

    • If your workplace already issues S/MIME certificates for email, you can often use the same cert to sign PDFs via desktop tools that hook into your OS certificate store.
    • Slight disagreement with the “just get a cert” advice: in practice, getting a personal signing cert from a commercial CA as an individual can be a hassle and overkill unless you really need formal legal nonrepudiation. If your org doesn’t provide one, I’d start with robust “scribble” signatures plus strong internal process before fighting with CAs.

If you want something dead simple and non-cloud:

  • On Windows only, the built-in Microsoft Edge PDF viewer lets you draw a signature and save the PDF. Not a real digital cert signature, but for basic HR docs it’s often accepted. Zero watermarks, nothing uploaded.
  • On macOS, Preview lets you create and reuse a handwritten-style signature from trackpad or camera, then stamp it in PDFs. Again, not cert-based, but very clean and fully offline.

Practical split I use myself:

  • High compliance / external contracts: a national eID or workplace cert + a desktop signing app or Acrobat Reader “Certificates.”
  • Everyday NDAs, internal forms, vendor docs that are more about convenience than court-level crypto: Preview / Edge / Xournal++ for drawing or image signatures.

Also, I’d completely skip:

  • Web tools that brag “free” then give you 3 documents a month and hold the rest hostage.
  • Any site that won’t clearly say where the file is stored, how long, and whether they use it for “service improvement.” That is marketing code for “we poke at your docs.”

So: if you say what OS you’re on and whether you actually need certificate based signatures for legal reasons vs “looks signed and everyone’s fine,” it’ll narrow things down a lot.