Issues with editing

I often use adobe to edit and combine files to submit for projects.  Typically i will ope two or more files edit then drag pages back and forth to put in order and combine between documents.  This is usually done with no issues but lately i have to close all the way out and bring documents back up because adobe loses the fuction to combine and even edit. Its weird i may go all day and then all of the sudden it just shuts off until i close out and open all back up.  

Any ideas as to why this is happening??