Rotate incrementally

I have macular degeneration (the dry kind) and can’t read a book except with strong reading glasses which strain my eyes. I scan some books and then I can read them on the computer. I get the pages lined up fairly well but would like to make a couple of instruction books look more professional. With the programs I have I can rotate the pages only increments of 90. I have been using an old free version of Infraview. Before ordering anything I thought I would come to the experts for suggestions. I do want to be able to keep them in a .jpg format. Perhaps my best bet is to upgrade Irfranview

Sparks