On the download page you have linked to, at the left, it has a link to Documentation
which leads to
- Introductory Documentation
- User Manuals
- Release Notes
- Knowledge Base
- UNIX man pages
Did you try that?
On the same page, there is a link to their Technical Support:
Try Our Technical Support During Your Evaluation
Evaluate Perforce. No one should purchase an SCM system without trying it out first. Download our free, fully-functional, unlicensed version of Perforce.
While evaluating the product, try out our Technical Support, too, and prove for yourself that we deliver the support you'll need to use Perforce in your organization
By all means let us know how you get on.