What paper type should fillable genealogy PDFs be printed on?

We recently received an email from a customer of our fillable genealogy PDFs. The question: What's the best paper type for fillable genealogy PDFs?

For EasyGenie 8.5 x 11 genealogy kits that we sell on our website, the paper stock our local supplier uses is 28 pound Hammermill Acid-Free Stock. Our customers love the quality. Here are some typical comments:

"As I go through old papers, most don’t hold up well. I feel like the quality of these products is worth every penny."

"The paper is sensual ... nice touch, and it loves ink, tape, and thumbtacks."

However, I am not sure if this commercial-grade paper stock is available from retailers. We source it through our professional printing partner near Boston, but when I looked for the same paper on Amazon and Staples I couldn't find it.

If you can't find the acid-free variety, we recommend the Hammermill 28 pound premium laser print available on Amazon. To check whether the paper is acid free, look at Hammermill's Amazon detail pages or go to the Hammermill website to determine which products are truly acid free. Hammermill is a great manufacturer and they provide accurate descriptions and specifications on their website for the best paper types. 

Another consideration in addition to paper type and composition: The quality of the machine that prints the PDFs. While you can purchase high-end home printers, for the best results turn to professional print shops in your area who may also offer framing and other services for your genealogy charts.