Q:

Is it possible to edit a PS file in view mode in ISPF? 

We can edit a JCL file in ISPF when we open a file in edit mode.  Is is possible to edit a file in view mode ? 

A:

View is basically Edit with out the save command. 
You can still use Replace command to over right a dataset/member with what you are editing (provided you have access and you are viewing an actual Dataset). 
You may need to put c9999 in the line-number on the first line of the File. 
Alternatively you could:

Use the Cut command (put c9999 in the line-number on the first line)
enter the edit command
delete the contents
do a paste
save and exit
exit view 

Why not simply edit the JCL in the first place ??? 