Didier Stevens

Sunday 4 January 2009

Howto: Add a Digital Signature to a PDF File

Filed under: Encryption,PDF — Didier Stevens @ 21:47

After signing an executable and a Mozilla add-on, let’s sign a PDF document with our certificate.

I didn’t manage to use a free tool to sign a PDF document with a certificate, so we’ll use a trial version of Adobe Acrobat Professional.

Our PKCS12 file (with keys and signatures) is imported in our certificate store, so let’s open a PDF document and sign it:



After signing, we notice there’s one issue, our identity is not yet trusted:


Let’s trust ourself:





After validation, Adobe Acrobat tells us our signature is valid:



  1. Thanks, this was helpful 🙂

    Comment by jamie — Tuesday 6 January 2009 @ 2:12

  2. […] a recent series of blog posts, Didier Stevens has been demonstrating how to add digital signatures to a variety of file types. Last week he covered PDF: the tutorials is relatively straight-forward, […]

    Pingback by How-to: Add A Digital Signature To A PDF File | 4xPDF Blog — Sunday 11 January 2009 @ 23:10

  3. I have forgotten my password for my electronic signature and I want to reset it how do I do it?

    thank you

    Comment by christal quigley — Wednesday 14 January 2009 @ 20:30

  4. If it’s a commercial certificate you acquired, you’re the only one who has the password to your private key.

    Comment by Didier Stevens — Thursday 15 January 2009 @ 9:33

  5. How can I use a server based signing of a pdf file using a web based digital signature? Any insights or pointers would be helpful. Thanks.

    Comment by Dr. D. Punia — Wednesday 15 April 2009 @ 18:30

  6. No sure what you’re asking, can you give me more details?

    Comment by Didier Stevens — Friday 17 April 2009 @ 21:34

  7. D. Punia, have a look at: http://www.globaltrustfinder.com/ZerofootPrintSigningStep1.aspx which does exactly what you mentioned i.e. signs a PDF where the digital id is held at the client side.

    Also if some one wants an advanced way of signing the PDF document e.g. multipage signing, designing of signature appearance, creating of blank empty fields then try PDF Sign&Seal: http://www.ascertia.com/Products/pdfsignseal/Default.aspx?m=menudocsign&s=pdfss

    Comment by Wahaj — Thursday 2 July 2009 @ 5:33

  8. […] then you could not sign on the pdf. If it is allowed then the step to sign are here , https://blog.didierstevens.com/2009/01/04/howto-add-a-digital-signature-to-a-pdf-file/ Tweet This entry was posted in General IT and tagged ID by admin. Bookmark the […]

    Pingback by Adobe pdf digital signature configuration | SQLTalk.net — Monday 25 July 2011 @ 5:09

  9. how to sign thousands of pdf by digital signature

    Comment by Anonymous — Thursday 20 December 2012 @ 5:25

  10. […] is an update to my post Howto: Add a Digital Signature to a PDF File, but this time I found free […]

    Pingback by Howto: Add a Digital Signature to a PDF File – Free Software | Didier Stevens — Friday 26 April 2013 @ 12:58

  11. hi i need to e file a document on MCA site a form which needs to be digitally signed but despite of following the above steps it shows ” one of thesignatures requires to be verified.. is this due to acrobat version ? or some other problem

    Comment by Anonymous — Tuesday 21 May 2013 @ 9:23

  12. @Anonymous What certificate did you use?

    Comment by Didier Stevens — Thursday 23 May 2013 @ 18:25

  13. What is a .pdf.sig file and how is this generated from a .pdf

    Comment by Anonymous — Saturday 19 July 2014 @ 16:10

  14. @Anonymous Do you have a .sig file?

    Comment by Didier Stevens — Sunday 20 July 2014 @ 10:07

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