Encrypt and Digitally Sign PDF

[aspec.451]

We are attempting to digitally sign and encrypt a pdf document. To do so we are
1) encrypt the PDF document using the "Secure PDF tool" and create a password to modify the document contents
2) save the document as incremental updates are not compatible with document security changes.
3) attempt to digitally sign the document using the "Add Digital Signature" tool
However when we try to encrypt the document it tells us "Operation not permitted for document".

We've reversed the process and digitally signed the pdf and then tried to encrypt it. That process fails with the error code "Unsupported operation".

I run into an issue when I follow the process in PDF-XChange Editor:
1) secure the pdf
2) save the document and close it
3) open the document
4) attempt to digitally sign the document.
To do this, I first need to remove the document security and then sign it.

I am wondering if we are not able to do this in PDF-Tools because after it secures the PDF it "closes" the document and then "Add Digital Signature" is unable to get past the modify password. We send out a large amount of PDF's and it would not be possible to manually encrypt and sign each PDF inside of PDF-XChange Editor. I've tried to create a custom tool that encrypts and adds the digital signature using the process:
1) Ask for Source Files
2) Secure Document
3) Save Documents
4) Add Digital Signature
5) Save Documents

However this still does not work. Is there a way to encrypt and then sign the same PDF document using PDF-Tools?

Thanks!

[Vasyl-Tracker Dev Team]

Hi, aspec.451.

We reproduced this issue and will fix it in the next build.

The valid sequence of actions will be:

1) Ask for Source Files
2) Secure Document
3) Add Digital Signature
4) Save Documents

OR

1) Ask for Source Files
2) Add Digital Signature
3) Secure Document
4) Save Documents

- each sequence will work as well. Please wait for new build.

About other sequences, that contains "Save Documents" between "Add Digital Signature" and "Secure Document":

...
- Add Digital Signature
- Save Documents
- Secure Document
...

- this sequence is incorrect because technically is impossible to set password security when document is already signed or certified.

...
- Secure Document
- Save Documents
- Add Digital Signature
...

- this sequence is may work only if document changing is allowed by security permissions.

=======

Cheers.