As much as we, BookCrossing, endorse the freedom of books and sharing them, as much do we respect the copyright rights of their authors.
Distributing digital copies usually is not only neglecting the authors' rights but it's also illegal in most jurisdictions, including the U.S. (home of bookcrossing.com), Germany (home of the distribution site you're using) and most likely Portugal as well. Apart from general fairness considerations promoting this through bookcrossing.com could seriuosly harm BookCrossing in itself as it could trigger legal actions against bookcrossing.com.
Since there's no evidence to us that you are holding the right for the books that you are making avl through digital download for the time being we've removed the corresponding links and we plan to also remove the full threads soon.
If you indeed are in the possession of the relevant rights, please don't hesitate to contact us throgh the "Contact" link on the very bottom of every bookcrossing.com page. In that case we'll happily revert our decision and accept you to add the links again. However, we would ask you to provide some indication directly in these forum threads in how far you're holding the relevant rights.
We've also noticed that you never registered a single book with BookCrossing. Therefore we're not sure you're familiar with the BookCrossing idea at all ...?