Some ideas for a downloads page requiring registration...

[velden]

You might want to have a look at ListIt2 http://dev.cmsmadesimple.org/projects/listit2

Create a list with all the needed information, maybe one extra field for picking a file is enough (Name and Alias are already there and required).

Then you could create two templates; one that shows the name and links that all point to registration page. And another template that shows the links that point to pdf files.

Dependant on the result of the cookie value (you need to read it with Smarty) you call the List module with summarytemplate='x' or 'y'.

[psy]

I did something similar with CMUsers and CMSForms. CMSUsers allows you to register a user with an automatically generated password so all you need is a username (email) plus any profile fields, eg 'Name' in the form.

The user is sent a verification code and taken to the download section when registered. In your case you could put the CMSUser tag equivalent to the CustomContent tag to display/hide page content based on whether the user is logged in or not.