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How can I sign a digital document without needing to print it?


I am often asked to return a signed and dated copy of a pdf contract. The
only way I know to do this is to print it on paper, sign and date it and then
re-scan it. Is there some way do this (to create a replica of my signature, the
current date, and sometimes a printed version of my name) that doesn’t require
a scanner and printer and avoids the use of paper?

It’s possible, though sometimes it’s not as easy as we might like.

But aside from the technical aspects of what you’re attempting, the more
practical aspect is simply this: it might not be valid to do so.

And honestly, when it is valid, it kinda scares me.


We’ll start with the how.

You start by scanning an image of your signature. Just “sign” a white piece of paper, scan it at high resolution, and then using an image editing tool crop it and create a few copies at different resolutions. If you want to get fancy, set the background as transparent.

“You start by scanning an image of your signature.”

For reasons I’ll describe below, you’ll want to keep these files secure.

Ultimately, though, all these files are is an image, a picture, of your signature. If you get my weekly newsletter you’ll see that I “sign” my first name at the end with exactly such a picture:


Next, you’ll need to be able to edit the document you’ve received. There are various PDF editing programs out there, and most will allow you, at a minimum, to place, or copy/paste, an image into the PDF document and then save it. A couple of examples include the full Adobe Acrobat tool (not the reader, but the full Acrobat PDF creation tool) as well as Foxit software’s PDF Editor (they also make the free Foxit PDF Reader, but the PDF editor is not free).

And that’s exactly what you’d do. Insert the image of your signature, or copy it from your image editing program and paste it, into (a copy of) the original PDF document. Choose the right size of signature image so that it looks natural, and place it at or above the signature line in the document. Save the result, and you have a “signed” document.

For completeness: I’ve also heard of people playing games with screen capture software when PDFs are not editable. Depending on the software used, they capture “screen shots” of the affected pages, alter them as needed in an image editing program, and reconstruct them into a new document that they then print to PDF. After all that, though, it would just be easier to print to paper, sign and scan.

Now, the more practical aspect.

I need to preface this by saying “I am not a lawyer” – because, yes, we’re actually treading into some legal areas. These are my opinions and understandings, and not at all intended to be legal advice. Check with your own counsel.

With my behind thus covered…

I’ve always been under the impression that for many transactions a FAXed signature is as binding as the original.

That scares me.

Because everything we’ve done above to “sign” a document and send it along above with a copy of your own signature could be done using someone else’s signature. Scan a copy of their signature from public records or even a check, clean it up and crop it a bit, and you’ve got someone else’s signature that you could copy/paste into just about any document, and then FAX on.

Now, the good news here is that I think things are changing. In some recent cases when I’ve signed documents digitally, or offered to FAX in such a document, I’ve been required to provide the original as well. The bad news is that even a printed version with the digitally pasted signature is often accepted as valid.

Depending on the industry you’re in, the use of a digitally inserted signature image may not be understood and thus never even considered, may be understood and accepted, or may be understood and explicitly not accepted if detected.

The question boils down to: can they notice, and if they notice will they care?

And if it turns out they care, will you?

Finally, you can now see why I suggested you keep your scanned signature image secure. You don’t want someone else to use it. While it’s possible that someone could get your signature from other sources, there’s no reason to make it easy.

(One important clarification: a digitally inserted signature image is not the same as a digital signature. The former is simply placing a picture of your handwritten signature into a document, the later is a cryptographic calculation based on the document content and your cryptographic private key or certificate.)

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9 comments on “How can I sign a digital document without needing to print it?”

  1. OpenOffice(freeware) drawing program can be used to edit pdf files, but I believe-I’m not sure-you have to download a plug-in. It isn’t very sophisticated,but it would be enough for this type of work.

  2. Digital signatures will be the signatures of the near future. Using programs like GPG and PGP you can create a password protected digital signature which can be registered and thus you and only you can sign it with your digital signature. I think that will solve the problem of signing documents sent by email and posted on-line. Check out Leo’s article about that. We just have to wait till people adopt it more widely. I get digitally signed receipts from my cell phone company here in Germany.

  3. The advantage to the sender of using a scanned image of your signature and pasting it in multiple documents over time is that it gives you plausible deniability of its authenticity.

    You can always confirm its authenticity on any documents you so choose.

    The risk is to those accepting a faxed/scanned/emailed signed document as authentic. They could have a large hurdle to prove it was you who sent it and it was not altered by a third party after transmission.

  4. All of the discussion above (including Leo’s response!) misses the very simple answer — you can use Adobe Acrobat to digitally sign a PDF. It’s a very simple process, nothing special, no fancy keys needed. You can chose to include a scanned signature if you want to, but it’s not necessary. The real point of the digital signature is to verify that the document hasn’t been changed since you signed it. After you digitally sign it, any change whatsoever to the PDF causes the digital signature to indicate that the document’s been been changed. The process works very well. I’ve been using it for 7+ years, starting with Acrobat 6. I haven’t physically signed or faxed a PDF contract in all of that time. The legality of a digital signature (in the Acrobat sense) was established during the early-to-mid 1990s, so it’s trouble-free.

  5. Leo wrote:

    I’ve always been under the impression that for many transactions a FAXed signature is as binding as the original.

    That scares me.

    Because everything we’ve done above to “sign” a document and send it along above with a copy of your own signature could be done using someone else’s signature.

    With a standard “IANAL, BUT…” disclaimer, I add:

    Don’t be so silly, Leo! That would be forgery, which the true owner of the signature could legally disclaim.

    It would also net the forger some very hefty jail time!

    I’m not saying that the true owner might not win – but that will require forensics to determined the forgery, legal involvement and perhaps even legal proceedings. I’m still scared, since that’s very painful, even if I win.


  6. You can use a program like Zosh for the iPhone which let’s you sign and return a document all from your phone. It’s pretty cool actually. You forward the PDF document to the Zosh secure server. Then load it up on the iPhone in the Zosh app. Then use your finger to sign. You can move, resize and even rotate the signature to get it exactly where it needs to be. Then just email it back to yourself, or where ever it needs to go. It comes out as a standard PDF with your signature in it. You can also add text, dates, etc.. Zosh is $2.99 in the App Store on iTunes.

  7. Yes. This is where an e signature system comes in handy. You don’t need to print out the documents. Rather, the transaction will be done on the cloud. If you give your clients the option to authenticate the documents you need online, there’s no hassle as you save on time and the need for a ton of paper. Your business then becomes customer and environment friendly.

    I’d love to know if this technology is accepted in court. The courts are generally lagging – and of course it varys from country to country. I’d want to make absolutely sure that any digital signature was accepted as legal before doing this.


  8. I have always used a graphic tablet in the past, but it’s a bit of a waste if you’re only getting it for this purpose, and on top of that, for some people, it just doesn’t feel right compared to holding a pen in their hand.

    Scanning all the way in this case.


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