OK.
Here's the preliminary result for the first (Cover) page in the template.

The part inside the thin black rectangle is the finished size. I used Oversize Tabloid as the sheet size (12x18") and centered the page on that. Your printer may want this size to allow for trimming the pages. If not, use Tabloid (11x17), and ignore the black rectangle shown here (not part of the finished page, and not used in the revised procedure listed below).

I would start by making a duplicate of the file, then work with the copy, not the original. That way, if you make an error (or if I did) you'll have a quick route back to the original.
Here are the steps:
- Open the copy of the document.
- Go File > Page Setup.
Set Format for: to Any Printer
Set Paper Size: to Tabloid Oversize
Click OK
- Open the Inspector. Go to the Document Inspector.
Set all four margins to 0.5 inch. Set Header (position) to 0.75 inch.
- In the document, select on object, then press command-A to Select All (of the objects).
Go Arrange > Group to group all objects (except the header box with its text) into one object.
(This should create a separate grouped object on each page. You can scroll down to check.)
- With all of the grouped objects selected, go to the Metrics Inspector.
Set Width to 17 in, Height to 11 in, and both position values to 0.5.
- Go Arrange > Ungroup to ungroup the grouped objects and make them individually editable.
At this point the basic resizing of the document is completed. You will likely need to do some tweaking. Individual graphics may require re-shaping to remove the 'NFL Lineman' appearance of people in photos stretched this way. That should be fixable by reinserting the original graphics files into the media frames. This will remove the stretch, but more of the original image will ve visible. Text size will not have been changed by this resizing. That requires resetting the font sizes. Text will also flow differently in the larger text boxes.
Regards,
Barry
Message was edited by: Barry Added two sentences to last paragraph.)