Which files (.indd or .idml) do I use to package and export them in and how to do this?
You cannot package .idml files, you can only open them, which will convert them into .indd files when saved.
2. How do I package and export into PDF and For Print "with the covers"? Should the covers also be in the Book Panel? They should be in the same folder, right?
For this you should talk to your printer. If you want all files packaged into one PDF you can use Acrobat to combile the files or add the cover to your book file and export the entire book as one PDF. Where files are when you combine them into a book is irrelevant. InDesign will keep track of the files’ locations so long as you con’t move them. When packaged everything will be combined into one folder.
If you are using the same link (like a logo in Illustrator) in multiple files make sure you are always linking to the same file. I often see people collaborate and use a book to package the work at the end. WHen this happens each InDesign file might be in a separate folder, far from its siblings, and each might have its own links file, meaning some images are used multiple times. When packaged InDeisgn will treat each instance of the link as a separate image nad package them all together. When this happens the copies are renamed so nothing is overwritten and hte links are corrected to match the renamed files. The result is a Links folder containing files like Logo.ai, Logo-1.ai, Logo-2.ai.
... View more