I have several PDF files in iBooks. I want to open them with the "PDF reader" App instead. How do I do this?
Another method, simpler, not involving clouds is as follows:
- Touch and hold on book's icon in iBooks, and, from pop-up menu choose "Print", see figure below:
Solution for MacOS (the question originally didn't specify OS)
To do this, just open the folder which contains your iBooks, right click on a particular book, go to "open with", and choose the program you want (say pdf reader).
This post describes where the iBooks folder is located in Sierra.
The OP has now specified that the problem is specific to iOS. Doing this directly is impossible due to the way that the iOS manages storage. iOS doesn't have a file system in the way that macOS does. Each file is associated with the operating system or a particular app. According to this website for iOS developers
For security purposes, an iOS app’s interactions with the file system are limited to the directories inside the app’s sandbox directory
This means app A can't just go into app B's storage and read a file (say a PDF document).
Thus, you need a workaround. Personally, I use google drive to sync my books (wirelessly) between my mac and my iPhone/tablets. While you could probably do something like this with iCloud I haven't tried that yet so I'll give my solution. All you have to do is
- Sign up for a google account if you don't have one already
- Download the Google Drive macOS app
- Make a folder F of all your books (iBooks already did this (see my unedited answer)). Then you have 2 choices:
- Choice 1 (ADVANCED): "Hard link" folder F to your Google Drive folder. This will update your google drive automatically every time F is edited, say every time you add a new book to F. The way to do this is discussed in this question. You will need knowledge of the command line.
- Choice 2 (SIMPLE): Manually copy F into your google drive folder. (Note that you can also drag F into the google drive folder. HOWEVER if you do this once F is uploaded, F will be stored in the (google drive) cloud, and no longer on your computer.)
- Download the google drive app on your phone (or tablet or android) and sign in.
- You can now see the folder F on your iphone and any other ios (or Android!!!!!) devices on which you have installed the app.
- If you have a wifi connection, you can just click on a PDF to open it. If you want to make it so that in the future you can open PDFs without a wifi connection, just follow these instructions.