Adobe Acrobat Reader (64-bit) 2025.001.20435 creates invalid digital signature

[jan_3791]

I signed 5.pdf as 5b.pdf on Windows 11 using Adobe Reader, and Adobe itself reports that the signature is invalid.

It used to work normally...

I also created 5c.pdf using Reader, but on Windows 10, and that one is fine.
Both have the same version...

I even deleted the signing certificate from the keystore on my Windows 11 and re-imported it.



A visual signature in pdf looks:

Signature validation is

I made it on Czech Windows, en translation follows ...

Image 1 (signature properties)

Signature is INVALID.
Signing time: 2025/04/15 15:06:51 +02'00

Signature details:
The signature was created using Adobe Acrobat Reader (64-bit) 2025.001.20435.
Hash algorithm: Not available
Signature algorithm: Not available

[jan_3791]

Size of 5b, 5c.pdf diffres even a same digital signature used and no timestamp:

[Tariq Ahmad Dar]

Hi @jan_3791, 

Thank you for reaching out with your question and sorry for the troubled experience.

Is this a certificate-based signature? Is this certificate added to the Windows Trusted root, for more information on that, please check this Microsoft help page: https://adobe.ly/3Ei6DLp

Also, if the signature was already created, has anything changed? For example, does the certificate still have validity if you are using it for the signature? 

~Tariq

[jan_3791]

The certificate I've used was the same on Win10 and Win11. On Win10, sig. properties are following

So the cert chain is OK. PostSignum is one of QC Service on EU TSL list. And yes, I have it in my trusted root auths.

The problem of 5b.pdf is
"Tento podpis je neplatný, protože se vyskytly chyby ve formátování nebo v informacích obsažených v tomto podpisu."


translated to EN:
"This signature is invalid because there were errors in the formatting or in the information contained within the signature."

After clicking on verify signature, I can see

Something about BER encoding of a signature. So the Reader on Win 11 is buggy and on Win 10 the same version and the same pdf and the same cert works fine and creates a little smaller file after pdf is signed.

[jan_3791]

Adobe created a signature of zero length:

<</ByteRange[ 0 61548 94466 13186]                                         /Contents<00000000…000>/Filter/Adobe.PPKLite/M(D:20250415150651+02'00')/Name(Jan Vávra)/Prop_Build<</App<</Name/Adobe#20Acrobat#20Reader#20#2864-bit#29/OS[/Win]/R 1638656/REx(2025.001.20435)/TrustedMode true>>/Filter<</Date(Mar 13 2025 01:40:24)/Name/Adobe.PPKLite/R 131104/V 2>>/PubSec<</Date(Mar 13 2025 01:40:24)/R 131105>>>>/SubFilter/adbe.pkcs7.detached/Type/Sig>>