Advanced PDF paper size / page structure questions

[Mayo5E89]

I scan a lot of sheet music that comes on 9" by 12" and/or 12" by 18" paper.  An odd size to be sure.  The scanning bed only allows for scanning 9" by 12".  What is the most ideal software to then stitch two or more 9" by 12" PDFs into an 12" by 18" PDF?

Then, I know I can easily use acrobat to take a little bit off the top and bottom to get the page size to the 8.5 by 11 aspect ratio.  But, is there an easy way to then reduce the size of the entire PDF down to 8.5 by 11 or 11 by 17?

Thanks!

[Luke Jennings3]

Photoshop. Go to File> Automate> Photomerge.

I would place the combined image into an 8.5 x 11 InDesign page, where you have good control over size and position, and export to a PDF.

Another option would be to use an Acrobat preflight profile to change the page size to 8.5 x 11.

Tools> Print Production> Preflight> Fixups.

[Dave__M]

One of the super-handy features of Acrobat/Reader is to print any size page to fit to the printer's printable area. In the screenshot below, I have a huge score printing to letter size... with a click of the mouse.  With this setting, large pages are reduced to fit, and small ones are enlarged to optimize the paper size.  This setting may prove helpful.  I use it for printing music all the time.  With this solution, there's no need to reduce the page size, but your situation may be different.

My best,

Dave