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I need to sign a PDF document. However, Adobe Reader does not let me sign documents. I just need to sign the document, not edit it.

Do I need to buy the full Acrobat software?

Or is there a better, simpler way?

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Acrobat Reader is now called Adobe Reader. –  Rowan May 4 '10 at 6:44
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There is some confusion on what you mean by Sign below.. Are you referring to signing as adding a picture of your physical signature to the document? or are you referring to stamping your digital certificate to the document? –  Brian Jan 27 '11 at 16:50
    
I'd rather wash my mouth out with soap than use that A word for compressed, dried mud. It reads Acrobat PDF. Acrobat Reader XI now does allow signatures, see answer below. –  Fiasco Labs Dec 16 '13 at 5:23

12 Answers 12

You don't need to buy the full Adobe Acrobat software to digitally sign a PDF file, but you will need to use a tool like Quick PDF Tools, Nitro PDF, etc. If you just need to sign a PDF file as a one off, then these products offer fully functional 14 day trial versions, which would let you sign the file.

Alternatively, you could programmatically digitally sign a PDF file.

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Ancient Question trumped by passage of time...

Acrobat Reader XI allows for signing documents by several methods including a scanned image.

enter image description here

You can then send the signed document by Email, Fax, have other sign or simply save a copy.

The file now has the signature included within it. You don't even need Acrobat itself, download PDFCreator from SourceForge to generate your document that needs to be signed, send it to the person needing to sign. They open it in Acrobat Reader XI, attach the signature and send it back to you for printing for your records.

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Assuming that the PDF doesn't have security preventing you from doing so, you may open the PDF with LibreOffice Writer (https://www.libreoffice.org/), and then paste your signature image onto it. It can then be exported as a PDF with the signature attached. I wrote a blog post detailing the full process in Ubuntu over at http://colans.net/blog/signing-document-image-ubuntu-1210 . It should be quite similar with other operating systems.

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Trying to open a rather simple, text-only, 9-page PDF with Libre generated a "General input/output error". The same document loaded fine in PDFEscape. –  Dan Dascalescu Jun 14 '13 at 21:14
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"Pasting a signature image" does not constitute a digital signature, which are generally cryptographic in nature. –  Dai Sep 9 '14 at 4:02
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@Dai: True, but that wasn't a requirement in the question. This is basically a shortcut to printing it, signing it with a pen, and scanning it back in, which is generally what folks are after. With this method, you also maintain the digital text within the PDF, which is good for searching through it. –  colan Sep 9 '14 at 14:16
    
While not a cryptographic digital signature, that method would probably meet the electronic signature act in the US meaning it would carry the same legal weight as a handwritten one. –  Dan Jul 19 at 20:57

In our adobe we create stamps by scanning our signature. You can use the stamp to 'sign' the document. You can create any custom stamp you want.

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In Adobe Reader Pro XI (note there is a time-limited fully-functional free trial), open the PDF, go to

File → Save As Other... → Reader Extended PDF → Enable More Tools (includes form fill-in & save)...

And then you get a PDF file that looks just the same, but will have all those other options no longer greyed-out when opened in the free Adobe Reader. This includes both handwritten "ink" signing and digital signing, various drawing annotations, etc.

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@Sathya What about my rant regarding senseless evil? How will Adobe realise they have a problem if we don't point it out? –  Evgeni Sergeev Aug 17 at 4:23
    
you can rant about it in your blog/Google+/wherever, we'd prefer to have answers contain just that - answers. –  Sathya Aug 17 at 4:31
    
Alright :) Adobe devs please check the edit history. –  Evgeni Sergeev Aug 17 at 4:42

You should be able to do it in reader, as long as the file isn't read-only, or locked.

Go to Document->Sign

If it's greyed out, you're out of luck whether it's the full version or not. Go to Document->Security->Show Security Settings, and look under the Security Tab. In the "Document Restrictions Summary" it will tell you if the creator of the document checked the box to allow it to be signed. If they didn't, you're going to have to re-render the document somehow.

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No, you cannot do this in Adobe Reader unless the PDF has been specifically processed in Adobe Acrobat to enable extended features in Adobe Reader that would allow the user to digitally sign the PDF. It does not sound like the PDF has been processed in such a way in this scenario. Note: only Acrobat can enable these extended features in Adobe Reader. –  Rowan May 4 '10 at 6:40
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No, many PDF creation tools can add a signature line. We use Nitro PDF and Bluebeam, and add signatures with both. However, for this to work, each computer needs a PKI certificate installed on it. –  Brian Jan 27 '11 at 16:49

I think this blog will help you out a lot: How to sign a pdf document

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If you need to just add the image of your signature, and perhaps fill in your name as text, then the absolute simplest way is to upload the PDF to pdfescape.com, upload the image, then download the PDF.

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pdfescape is dangerously insecure as they don't even use SSL for either your documents or login credentials. See my answer about pdfbuddy.com for a much better online alternative. –  Yarin Dec 16 '13 at 15:00

You can easily edit and sign your PDFs online with PDF Buddy (www.pdfbuddy.com) - it lets you add signatures as images or by drawing on the screen. Works anywhere, nothing to install.

(Disclosure: I'm a co-founder of PDF Buddy)

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You can use Inkscape to draw your signature into PDF documents.

Advantages include: (1) it works cross-platform (Linux, Windows, OS X), (2) it is free software, (3) does not rasterize the PDF, (4) minimal file size by saving the signature in vector format, (5) allows pressure-sensitive variable width writing with a pen input device, giving the signatures a more authentic / natural look (6) works offline, (7) quick & easy signing directly in the document (while saving a "blanko signature" to insert as image would appear untrustworthy if you want others to sign a receipt etc. on your computer), (8) resulting PDF files are often considerably smaller than before, without quality losses, (9) smoother mapping of pressure to pen width than Xournal.

Caveats include: (1) more difficult to set up and use than Xournal (2) needs additional steps to sign multi-page PDFs, (3) might mess up complex PDFs.

Configure input preferences

These steps are only needed once:

  1. Under "File → Input Devices … → Configuration", enable your pen device, enable "Use pressure-sensitive tablet (requires restart)", click "Save", and restart Inkscape if required.

  2. Select the calligraphy tool (Ctrl+F6), and in the toolbar select the options "Width: 4", "Use the pressure of the input device […]: Yes", "Trace the Lightness […]: No", and set all further options in that toolbar to "0". In the left of the toolbar, save this as preset "Signing Pen (A4)" or similar.

  3. Draw any object, set its fill to "black", stroke to "none", and select it.

  4. Double-click the calligraphy tool, select "Create new objects with: This tool's own style" and click "Take from selection". Also enable "Width is in absolute units".

Usage

  1. Open your PDF in Inkscape. In the options dialog, select the page you want, select "Text handling: Import text as text" and disable "Replace PDF fonts by closest-named installed fonts".

  2. Zoom in (F3) on the signature field, so that the intended signature size is roughly the size of your handwriting.

  3. Use the calligraphy tool (Ctrl+F6) to draw your signature.

  4. Click "File → Save As …" and enter a filename, selecting "Portable Document Format (.pdf)" as format. In the next dialog, disable "Convert text to paths", enable "Export area is page", and click "OK".

  5. To sign multi-page PDFs you can use pdftk to replace a page with your signed version of that page that you created above. See here for instructions.

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You can use Xournal to draw your signature into PDF documents.

Found it after recommending Inkscape in my other answer, and for signing PDFs "quickly and cheaply" it's much better. Advantages include all those of the Inkscape solution incl. vector-oriented signatures, plus: (1) no-fuzz configuration of pen and pressure sensitivity, (2) no extra steps for signing multi-page PDFs. The disadvantage is, it's not as cross-platform (mostly made for Linux).

To install Xournal under Debian / Ubuntu Linux: sudo apt-get install xournal

To use Xournal:

  1. Start Xournal and use "File → Open" to open your PDF.

  2. Select "Tools → Pen", "Tools → Pen Options → medium" and (if you have a pen input device) "Options → Pressure Sensitivity".

  3. Draw your signature into the document with the mouse or pen.

  4. Use "File → Export" to save back to PDF. Xournal's own format .xoj is not applicable for data exchange.

Source: Inspired by this and this related answer.

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Assuming you mean "sign" in the sense of writing your name on it (rather than in the sense of a digital signature), the absolute simplest would be to print it, sign it with a pen and scan the signed document back into a pdf.

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