Is there a way to convert a normal 8.5 x 11 manual into a 8.5 x 5.5 booklett?
We have done this with a new template, but it seems that there should be a way to convert the manual electronically instead.
Open both the existing document and the smaller template.
In the large/old document...
File > Import > Formats
Import from Document: [template.fm]
[*] Page layouts
Or was this question actually about imposition?
If you're asking about imposition, rather than simply changing the size of your document, then you need to use software that allows imposition. Typically, you create a PDF and then impose the PDF to get a booklet layout. Some printer drivers can also do this.
If you search for PDF imposition tools, you will get a plethora of hits. Many of these are meant for commercial print shops and would be overkill for the average FM user. I use Quite Imposing Plus for my needs.