Adding a later signature to a signed document

[James5D25]

I need to sign a document and have my client sign the document. A copy of that digitally signed document then needs to be sent to a third party. After the copy of the digitally signed document is sent to the third party, I need to add an addititional signature to a page of the document (attesting to the fact that I sent the documnt to the third party) and then have the final document with all three signatures, my original signature, the client's signature, and my second signature.

Is this possible? If not, this is a fatal flaw in design because there are many instances where a digital signature needs to be added to the original signed document later, but the document also needs to be available before that final signature is added.

[Graham5E57]

I am trying to sign a Bank Account Application Form, and I am advised by the system to take a picture of the signature with my phone , upload it to the PC, and then drop it into the relevant box.   I have done all this without a problem, but when I drop it into the box I get a message that Adobe Acrobat Reader could not open the file because it is not a supported file type or the file has been damaged.   I have tried this three of four times using differnet ways of creating the file picture but always get this message.   It's a .jpg file, and should work, but it doesn't.   Can you tell me what to do please?

[default9fbnacoxjfzf]

You have correctly identified another flaw in this software.   Many times one (especially in documents with multiple signatures from multiple parties) one may overlook a spot for a signature.  Apparently there is no way to fix this by simply adding another signature to a form that was previously circulated and signed (as it would be done using a paper signature).  Another frustrating unaddressed issue with the software is to also specify intials for recipients (for example, it is customary in many circles that each page is also initialed in addition to the overall agreement being signed).  
Unfortunately, the software development team needs to be supplemented by folks who actually try to use the software in real life.  Very frustrating that such basic functionality seems to not have been recognized.