can't print file stored on ReadyNAS

That is strange. My setup is very similar to yours. I have an HP MFP and HP Laserjet connected to the network and all of my files are stored on the NAS. When I open a file, I have no problems printing to either printer from any of 3 networked PC's.

Copy a word file from the NAS to your desktop. Then open the document in Word from the NAS and see what it says in the frame of the Word window at the top. Then close that document and open the document from your desktop and see if the info in the frame at the top is the same.

Now, that being said, I have had IP address conflicts in the past (when I attempted to print a document on the MFP, it printed on the LJ instead because for some reason they both had the same IP address - but that is an issue with the router). I have also lost connection to the printers on occasion (won't print anything in that case until after I turn the printer off and back on) but that is an issue with the printer drive on the PC.