Copying to desktop does not resolve the problem. The PDF attachments come from different sources. If we open the originally received document in Outlook it opens. But if we open the FWD version that was sent from an iOS device it does not. Is this a known issue with iOS devices and PDF in reader and acrobat?
Do you know which iOS mail app was used to forward emails with PDF attachments? (Acrobat Reader for iPhone and iPad itself is not an email app.)
There are known defects/issues with Apple's built-in Mail app.
Please see Problem #2 in the following FAQ document for more details.
In particular, please see the "workarounds" section for Problem #2. You can try removing your email signature, when you forward an email with any attachments (not just PDFs), if you are using the Apple Mail app on an iPad/iPhone.
Alternatively, you can use Microsoft Outlook for iPad/iPhone (instead of the Apple Mail app), if your company uses a Microsoft Exchange server for emails.
Hope this helps.