Thank you for posting on Adobe forums.
Could you please let me know what version of Acrobat you are using.
You can secure PDFs either by using password for opening the PDF or signing it. Please ensure that you are entering the correct password for your document.
Let me know.
Do I understand your problem correctly: You created a self-signed Digital ID (certificate) in Acrobat and want to use it to sign PDFs with this certificate? In the process of creating the Digital ID you were asked and entered the password for this Digital ID. It is this password that you need to enter in the process of signing with this certificate. If you misspell the password (it is case-sensitive) then Acrobat rejects it. It could be a case of some letters in the password lower/upper case mismatch.
If I misunderstood your problem, then please, describe it in more details.
You have restated the problem, and again, no matter how many times I change the password, when I go back to sign, it never works. I only use a few different password combinations for Adobe. The problem is that once I sign out, I can never sign a document again without creating a new signature.
The problem is that once I sign out, I can never sign a document again without creating a new signature.
Where did you sign out?