Acrobat Error when Requesting Signature

Yes margueritek, this would be an alternative but I cannot expect or restrict every of my intended signees  to register with Adobe. Its just not realistic.

Through experimenting however, I have discovered the much easier and secure steps to follow for a secure Signature Request:

1. Document/file to be sent for signature must have no security options activated before Sending for Signature.  Otherwise the Request for Signature process will indicate "unsupported file ... choose another file".
2. Once document/file has no security, click on "Send for Signature". In pop-up window click on "More Option" at the the bottom. That will open another window with several options to choose from.
3. In  "Recipients" box enter recipient email address. In the same box click on "Email" icon and choose "Password" where you have to fill in password. (you have to do this for each recipient).
4. Beside the "Message" box there is another box "Options" , click on Password Protect and fill in pasword (you can use the same or different password than previous one).
5. In the "File" box you will see the file name you are sending and have the option to add more.
6. Click on "Next" at the bottom, where you choose where you want document signed and any other fields you might request. 
7. Once all your requested fields are indicated, click on "Send". You are done.

Adobe will send intial email to recipent(s) informing him/her/them of signature request.

Nobody without the email password will be able to open/view or sign the document simply by clicking on the "Review and Sign" blue square in the email message or open any attachement.