The "Eurail Pass" is not sold through the CP sales channels, but can be acquired through the site.
The following passes are valid for travel in Portugal:
Eurail One Country Portugal Train in Portugal, seat reservation mandatory.
In Portugal, "Eurail Pass" are authorised to travel on CP - Comboios de Portugal trains , but they have to pay a booking supplement on the following trains where reservations are mandatory:
See the official Eurail site for further information Eurail, with information in different languages.
You can download the Rail Planner App, for Android or for iPhone, which has been especially designed by Eurail Group GIE.