I'm not sure of the pressure rating(s) for Pex, but I also haven't seen or read where Pex has been used for that purpose. I'm in the process of getting compressed air lines setup from my 80 gallon compressor, mainly to supply my plasma cutter but also for general use, and I'm going to use thick walled 1/2" copper tubing. The compressor outputs 175 psi so I'm filtering it first then immediately regulating it down to 90 psi which will be available at all the ports that I'll distribute in the garage. The air coming from the compressor will connected to the filter using a 1/2" rubber air line rated at 300 psi, so that will take are of 2 things - it's flexible so compressor vibrations won't cause stress on rigid connections and its pressure rating will easily handle the 175 psi output. BTW, the first device on the compressor is a 1/2" full throat ball valve so it won't restrict the air flow volume and the rubber line connects to the output side of the ball valve.
This copper tubing is surprisingly inexpensive when bought in 10-ft lengths and its working pressure is well below the 90 psi it will be used with. If you go this route, just be sure you check the rated pressure as there is a thinner walled tubing that isn't rated for high pressure. Here's a link to Lowes for copper tubing that meets the pressure requirements, at least for me. It's 10-ft long and has 200 psi max pressure rating.
Now, if you're trying to keep your air lines flexible throughout your shop, so you don't have to deal with corners and bends and such, you might consider using the high pressure rubber air line like I used. I simply searched Amazon.com for this and was really surprised how inexpensive this was too. It's available in several lengths and diameters.