If you just put a print into a frame without a mat or spacers contact with the glass can cause sticking buckling newton rings and a variety of other problems.
Framing a print without a mat.
If there is a border around the image that border will be visible unless you cover it with a mat or cut it down and get a smaller frame.
Like a mat floating gives the piece some space.
The trick is to use spacers to create an air gap between the print and glazing glass or acrylic.
Most framing experts agree that it is best to keep the pastel surface away from the glass.
When matting is eliminated the framing options are to either sandwich the painting against the glass an old french method or to utilize a spacer.
They should have told you get a frame the same size as the paper your print is being put on if you want easy cheap framing where no mounting is required.
Picture frames destination inc.
Second we use a spacer to create space between the plexiglass and the surface of your work.