Here's how to sync and save PDF files from your PC to your iPhone X's iBooks app:

1. After that, connect your iPhone to your computer and launch iTunes.
2. When your iPhone X or the iPhone symbol displays in iTunes, choose it.
3. Go to the Settings menu and select Books.
4. Choose Sync Books from the drop-down menu.
5. If iTunes is set to only sync selected books, make sure the checkbox next to the PDF you wish to sync is selected.
6. To begin synchronizing, click Sync.

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