It depends on where the paper was printed. US and Ca it's all soy-based ink. If it came from some other foreign country, I'd be suspect of it.

My husband has been in the printing industry since he was in high school. He says that while the soy base is safe, the pigments usually are not, being heavy metals. He is happy that I don't use the pages with color pictures, advertisements, etc.

You might pose the question on the Soil Compost & Mulch Forum for more detailed information.

Use it. Very few printers use heavy metals any more, because they don't want the hassle and expense of cleaning the presses and disposing of the inks.

The last time I had printing done we had two ink choices for one color, and one of them had a "clean-up" surcharge.