Problem after editing to print
 

Hi all I am having problems after I take my pictures and save them to my computer, I like to go in and play around with unique edits, however lately when printing them (even taking them somewhere to be printed) they are looking more grainy or pixelated. Some people said check the camera (I did highest setting available), others said maybe DPI or compression on the photo when editing using free programs. I would like to clear this up please please help.