c# - Can read file from local computer, but not from IIS server -

i've got mvc site i've published remote server running iis, i've got problem site can upload documents folder (on server, within site header folder) via site, "access denied" error whenever try read same document.

at first thought may have been simple permissions problem, checked security on folder , it's showing full control domain users on it, , when run project locally through visual studio can open without problems.

i assumed may context of site running under iis, don't know if changes need made in iis or on folder permissions themselves.

can help?

edit

i'm opening file using process.start like:

system.diagnostics.process.start("filepath"); 

edit 2

i've edited app pool site running on , set allow process interact desktop, has not worked. have tried setting app pool load user profile based on suggestions found elsewhere has not worked either. other suggestion i've found set app pool identity "local system", people have said security risk don't want unless necessary.