While the iPad can read PDF fine some tablets may not be able to handle them. EPUB format is more widely supported. EPUB tends to be 50% of the PDF size.

EPUB text can be scaled larger and smaller easily which PDF cannot do. This feature is very helpful for those with limited vision who need larger print. EPUB repaginates depending on text size which is why the Amazon Kindle is popular.

Thankfully open source has a solution. A tool called Calibre is available for Windows, OS X and Linux. This program can convert PDF to EPUB and it can even handle meta data so that author and title are preserved.

Apple Books on the iPad can read EPUB and PDF easily. Sime drag and drop onto the iPad in iTunes.