There is good information on the PayPal site. But, as someone who recently, painfully, implemented an almost-bilingual setup with PayPal, my suggestion would be for them to provide more linguistic capabilities for the international market.
We set up PayPal to accept payments for Translation World, a conference on the business of translation taking place March 11-13, 2008 in Montreal. Obviously, for a conference in Montreal, it is extremely important for all documentation to be in two languages. There was no way to select a combination of “Canada” and “French” for defaults. Mind you, we got around this by faking French signups as being from France, not Canada. Yet even though the first pages the users see will be in French, the final acknowledgement still comes back in English.
When we did research into the problem, we came across a complaint that the PayPal default language for Belgium is … English. I guess there is more work to be done.