Viewing PDFs that reside in the IFS of an AS400

I am trying to view some PDFs that reside in the IFS on an AS400.  I map a drive to the system, then drill down to the folder that holds the PDFs.  I click on the PDF to view, but Adobe opens up with an error, "There was an error opening this document. File already exists."  However if I use user QSECOFR when signing on to the mapped drive and drill down to the folder that holds the PDFs, I click on it and the file opens up.  Any idea where the security issue is residing?  I've already tried the preferences>general and the unchecked the box regarding the security, but it didn't work.