To adjust book templates for zero content books:
Export to Word
Adjust your page size to what you want and save.
Set the Margins to .6 all the way around
In that same section select Mirror margins for Multiple Pages
Select Apply to Whole Document.
Then go to print, select print to PDF
Click on Printer Properties
Change Default to: PDF/X-1a 2001
Pick what size you want in the last drop down -- if the size you want is not there
you can Add, then put in the size so for letter size you would put in 8.50 x 11.00
6x9 you would put in 6.0 x 9.0.. Note, Letter should already be in there but you can
save as many sizes as you would like for use later.
Hit Okay and Print.
This will enable you to use any template in any size you wish.