New to Adobe Acrobat & having digital signature issue

[jayn99]

I cannot digitally sign a specific kind of PDF in this new application. It's when 2 types of documents are combined.  
 
Situation:  
- Someone else has a PDF and an email which has been made into a PDF in Acrobat . They are combined into 1 document and saved into a file. 
- I come along and open that document of the 2 combined PDF's, and need to stamp and digitally sign it. I can stamp but cannot sign. I get 2 errors. 

. Unknown Error Support Information: CGetSigningParams-4069 

- Adobe Acrobat error. Could not find startx ref address. 

[AnandSri]

Hello @jayn99

I hope you are doing well, and we're sorry for the trouble you had.

Thanks for the clear description and the screenshots. Those two errors are:

“Unknown error – Support Information: CGetSigningParams‑4069”
“Adobe Acrobat error. Could not find startxref address.”

The second message indicates a damaged cross-reference (XREF) table or other structural corruption in the combined PDF. That kind of corruption is common when a PDF created from an email print‑to‑PDF is merged with a “normal” PDF, or when the file is saved with incremental edits and then further modified. When the internal structure is incorrect, digital signing fails even though stamping still works (stamps don’t require a certified/append-only update, unlike digital signatures).

Please ensure you have the latest version of Acrobat installed on the machine: 25.001.20997. Planned update: December 9, 2025. Check for any pending updates by navigating to Menu > Help> Check for Updates. Install the updates, restart the app and the machine, and try again.

Confirm it’s not a PDF Portfolio
Open the combined file and look at the top bar: if you see portfolio controls (files listed like attachments), it’s a Portfolio. Portfolios require a different approach. If it’s a single, linear document (pages, not embedded files), continue.

Test with a fresh save
Open the file > Menu > Save As (choose a new filename). Try signing that copy.

Use Preflight “PDF Fixups”

All Tools > Print Production > Preflight
Switch to Profiles or Fix-ups
Run these (in order, if available on your build):

Rebuild corrupted XRef table / Repair PDF syntax
Flatten annotations and form fields (only if you don’t need interactive fields)

Analyze & Fix > save the output as a new file > try signing.

Optimize & linearize

Menu > Save as Other > Optimized PDF

Let us know how it goes.

Thanks,

Anand Sri.