I offer this for what it is worth, not suitable for all applications but something to keep in the back of your mind.
For ages bookbinders have made an imitation vellum by painting both sides of a paper with blonde de waxed shellac.
I print using a regular inkjet printer and then treat the paper, the ink does not bleed, the shellac seals the ink and makes the paper waterproof.
There are full instructions for this simple process on my website. (gold-vault).
As I say, not suitable for every occasion, but if you want the look and feel of parchment, this method results in something far more convincing than mass produced parchment papers, and it also seals in the ink.