Hello @Ahadjilani,
I hope you are doing well, and thanks for reaching out. We're sorry for the trouble you had.
Are you using the Acrobat Reader mobile app on an Android device or an iOS device? Is it happening with all the PDFs, or is it specific to one PDF? Have you tried/tested with any other PDF file? Please ask the recipient to ensure the Acrobat Reader mobile app is updated and the latest build is installed.
Please ask the recipient for the workflow used to check the signature, and how the PDF file is being opened.
At your end, after signing in to the mobile app, tap Save / Done and reopen the file in the app. Ensure you can still see the signature yourself before sharing.
Share the correct file (not a preview link).
Let us know how it goes, and share your findings.
Regards,
Anand Sri.