Some (many) years ago, I equipped several (PDF) catalogs with an order form. There are different possible approaches.
In some cases, we added a checkbox, or a button "buy it", which then transferred the item number and description to the order form page, where the user had to enter the number of ordering units.
In other cases, we added a text field where the user could directly enter the number of items, which then triggered an entry in the order form.
The actual order form could either be part of the catalog document, or come along as a separate document, where a uni- or bi-directional communication between the documents is set up.
Prices are another issue. But even here, we got the possibility to enter/update customer specific prices. In other cases, no prices were included at all.
These projects were all done before InDesign allowed for "interactive" documents, and were using Acrobat Pro to author; these documents do work in Reader.
If there is interest to further discuss a possible project, please feel free to contact me in private.