Can other employees see my personal documents or salary?

NO, is the answer. 

Only the HR manager or the admin can see your data as an employee. Your colleagues can't see this information and won't know your compensation the same way you won't see anything personal from them. 

Only users who have a Manager, Administrator, or document viewing and editing permissions role will have the option to view the shared documents in your Profile. 

Factorial is a 100% secure HR software and your privacy is very important to us. If you have any more doubts about the privacy of your data, you can check out our Privacy Policy