Print your label on a good quality cotton office staionery paper, it's pH neutral, acid free, no lignins, etc. Good stuff for labels. Print the labels with a pigment based inkjet, or laser, if you can. Oherwise use plain inkjet, it's not giong to fade on the back of the mat. I like to give 'em a dusting of Krylon Fixative, the stuff artists use to prevent smudging of pastels, etc.

To glue it down, us wallpaper paste. I'm not kidding... just look for the past made of methyl cellulose (I'm pretty sure that's what it's called... I can't get to the box right now to confirm it.) This is not the old fashioned wheat paste whic bugs used to have lunch on. Methyl cellulose is a modified cellulose that is inedible to bugs, mould, and other such organic critters. Mix only 1/8 teaspoon in 2 shot glasses of water, and you can mount LOT of labels. Paint it on the label with a 1" foam brush.