Viewing Attachments. What Changed?

Hi there

Hope you are doing well and thanks for reaching out.

Is this an issue with a particular PDF file or with all the PDFs? Please try to open a different PDF file and check. 

It looks like this document contains a digital signature field, please make sure the users are signing the  document via Acrobat desktop application to complete the signature process https://helpx.adobe.com/acrobat/using/signing-pdfs.html

You may also share the PDF file in question so we can check it at our end.