I have spent a gruelling week producing a book from scratch using text edit documents, then adding images, hyperlinks, etc.
I got told last minute it will eventually need to be printed double sided (its been printed single sided for now for review).
The problem I have is that I have my page number on one side (outer) of the Master and a running header and chapter numbers the opposite side (inner), so if I print one page it will be fine, but the next page that would be printed the other side of the same piece of paper would place the number inwards by the spline (see picture).
Is there a way I can transform my chapter documents to print double sided, or do I need to start all over with Facing Pages documents?
If its the latter, whats the most logical way to do this? Copy and paste, etc.?
You can change your document to facing pages in the document setup. At that point, you could change your Master page to a two-page Master, but you could fix your alignment issue without doing that.
Once you have a facing-pages document, you could go to your single page Master, and stretch the text boxes for the page number so that they each cover the entire inner-margin width. Then set a paragraph alignment on the page number of Away From Spine, and on the Chapter use Toward Spine.
The text in the boxes will move according to its relationship to the spine. In the example below, each of the text examples are set to align away from spine.