When I am attempting to email a PO to someone, it cannot find the PDF at c:\ists\pdfs but that is where I have told it to save to (in US-A) but there is nothing there.  Is there somewhere else I need to tell it where to save it to?

In evosettings.ini, there are different sections for each user.  Make sure the particular user's section has Attach Path=C:\ISTS\PDFS\
 
Also, make sure the PDFS folder exists in c:\ISTS.