Possibility #1: The user is copying an original that is not the default size of 8.5" x 11" - OR - The user is copying an original and has set More Options > Original Size to something other than 8.5" x 11" (in either case, the MFP will want output size to match input size and will ask you to load paper matching the original's size).
Solution: Specify the output size. Go to More Options > Paper Selection and choose any tray that the machine says is loaded with plain (8.5" x 11") paper. The MFP will automatically reduce/enlarge the size to fit on the available paper.
Possibility #2: The user has intentionally set Paper Selection (if copying) or Paper Size (if printing) to something other than 8.5" x 11" because that's the size output he or she wants.
Solution: Our trays only have Letter-sized (8.5" x 11") paper. Users have 2 options:
use the Letter-sized paper
provide their own paper of the needed size and print/copy using the manual feed tray (Tray 1)
IMPORTANT! We offer LaserJet printers. DO NOT USE INKJET PAPER IN THE LASERJET PRINTERS. Inkjet paper will melt and damage laser printers.