Q: Adding PDF's to iBooks v1.5 will not show up in iTunes v12.3.3.17

Hi Mocha Media,

I understand that you are having some issues with your ability to sync PDFs from your computer to your iPhone. There are two ways to sync these items: through iTunes, or through iCloud:

Sync ePub, iBooks Author books, and PDF files with iBooks and iCloud - Apple Support

https://support.apple.com/en-us/HT205751

Use iBooks with PDF documents on your iPhone, iPad, or iPod touch - Apple Support

https://support.apple.com/en-us/HT202075

Hope this helps. Take care, and thanks for visiting the Apple Support Communities.

Hey again Mocha Media,

Sorry to hear that you are still seeing some issues. I have another suggestion for you. Try opening iTunes in safe mode using the instructions below:

Start iTunes in Safe Mode

When you open iTunes in Safe Mode, you isolate the program from any interference caused by plug-ins or scripts not manufactured by Apple. To start iTunes in safe mode, hold down the Shift and Control keys on your keyboard while you open iTunes.

You'll see a message as iTunes is starting that says "iTunes is running in Safe Mode. Visual plug-ins you have installed have been temporarily disabled."

If the issue doesn't happen in Safe Mode, remove any third-party plug-ins.

Fix unexpected quits or launch issues in iTunes for Windows - Apple Support

https://support.apple.com/en-us/HT203206

Ignore the fact that this article is intended to address iTunes for Windows, the safe mode procedure is the same on the Mac. Take care, and thanks for visiting the Apple Support Communities.