You'd have to make a concentrated solution of propylene glycol and alprazolam. Then you'd have to find a paper medium that would soak up all the PG without issue.
This will probably only work if you have straight alprazolam (ALP) powder which is hazardous stuff. I can imagine it would be easy to accidentally expose yourself to excess amounts and blackout, so if that's what you have be sure to be cautious and wear gloves when handling. If you have pills then it become problematic as the pill binders are going to probably make the alprazolam less soluble in PG.
I would make like a 10mg/ml solution so you only have to lay .1ml for 1mg blotters. You are going to need a precision eye dropper, pipet, or syringe capable of measuring very small amounts of liquid.
Personally i have never tried dissolving benzos in propylene glycol, you might have to add a little bit of heat and enthusiastic stirring to get the ALP to dissolve. Also i'm not sure exactly what kind of paper soaks up PG efficiently so you'll have to experiment with random papers and some plain propylene glycol.