Assuming you are using the latest version of iOS on your iPad or iPhone, and that you are using the latest version of iTunes and/or iBooks, syncing ebook (pdf) files should be a breeze!

If you’re using iBooks on a Mac, first drag the pdf file onto the iBooks window to add the ebook to your Library. The follow the instructions below:

1. Connect your iOS device to your computer
2. Open iTunes and select your device
3. Select Books in the left sidebar
4. Ensure that “sync books” is selected and choose either the “all books” or “selected books” radio buttons
5. If you select “selected books” you’ll need to select the individual eBooks to sync
6. Click the Sync button

If you’d like to sync your ebook to your iOS device from a Windows computer, follow the steps below:

1. Open iTunes
2. Drag the ebook into iTunes
3. This will automatically add the ebook to your iTunes library
4. To confirm, click the Book menu to check that it’s there
5. Sync your iOS device with iTunes

If you’d like an alternate method for syncing from a Mac or Windows computer, you may look into doing this via iCloud. Read more about this method here.