Saving PDFs - Error Message

We are having issues saving PDFs in a shared folder.

3 people in the office have the same folder open at all times (our incoming FAX folder). PDFs in this folder need to be viewed in the PREVIEW panel, and sometimes edited with ACROBAT. HOWEVER, no one can save anything unless everyone closes the Fax folder first. Very frustrating. If this was a word or excel doc, you could save no problem, but we all need the ability to edit PDFs and save them at any given time.

Any suggestions? I have tried enabling/disabling all the enhanced security features wit no luck.

Help!