Synching and updating issues with Adobe Acrobat PDF files

Hi,

We have a team in our Organization reporting emails (with specific PDF attachments) received on a specific shared mailbox, keeps reappearing in the shared mailbox Inbox after they filed it away. Issue is intermittent.

They also reported that notes saved on the same pdf attachments saved on a network file share gets removed after being reopened. Issue is intermttent as well.

We initially thought its an Outlook or network share issue but this is only happening to specific pdf files. I checked around and it seems similar issues are happening caused by Adobe Acrobat Reader. They are using Adobe Acrobat Reader X.

Please assist as this is disrupting a very crucial team in a big Organization.