How do I redirect users to a predetermined url after login?
All forms in Drupal support a internal destination parameter.

When you link to the user or user/register form, you can add ?destination=[url]

user/register?destination=node/1


Since you display the files-list with Views, you will need to re-write the files link to include the destination parameter.
If you output the link with l(), you can add the extra url data in l's third parameter like

l('Sign in to View', 'user', 'destination=node/1');