If you're thinking about the material:
* Modern paper: This is the most obvious choice, as parchment is an older material.
* Digital document: If you're talking about the form of the document, a digital document is the opposite of a parchment.
If you're thinking about the writing surface:
* Canvas: This could be an antonym if you're thinking about the texture or surface used for art.
* Stone: This could be an antonym if you're thinking about a material for writing or inscriptions.
If you're thinking about the historical context:
* Contemporary: This could be an antonym if you're thinking about the time period associated with the material.
Ultimately, the best antonym for "parchment" will depend on the specific context of your usage.