If they are already images, converting to PDF won't add things like text search and copy or scaling (that adds more detail), you'll just be using PDF as a flipbook.
If you want to be able to search and maybe generate indices of multiple issues, you might want to buy the full Adobe product and let it scan & OCR the text portions of the magazines.
I have no idea of whether Adobe is smart enough to offer mutli-PDF indices but it's at least possible to create them later if the text is stored as text instead of as jpeg pixels. Printing and view scaling should also be cleaner for text stored as text.