Thank you.
Could you address my question about what's best practice? What do most companies do?
I am not sure what the best choice would be for us -- to expose PDFs which compete with their own landing pages or not.
Also, do you know if PDFs pass SEO "juice" to the main domain? Even if they are hosted at www2.maindomain.com?
Where can I see some proof that this is the case?
If the PDFs have a canonical tag pointing to the parent page, wouldn't this be confusing for the search engines as these are two separate files with differing content? Canonical tags are usually used to eliminate duplicates for differing URLs with identical content.