Do I need to get a visa before flying to Peru and Bolivia for one month holiday?
Or can I just get it once I've landed there ?
I'm from Europe (The Netherlands).
No for both countries:
Peru:
With a few exceptions (notably some Asian, African and communist countries), visas are not required for travelers entering Peru. Tourists are permitted a 30- to 90-day stay, which is stamped into their passports and onto a tourist card, called a Tarjeta Andina de Migración (Andean Immigration Card), that you must return upon leaving the country. The actual length of stay is determined by the immigration officer at the point of entry.
Read more: lonelyplanet.com
Bolivia:
Citizens of most South American and Western European countries can get a tourist card on entry for stays up to 90 days, depending on the nationality.
Read more: lonelyplanet.com
I had no problem getting 90 days each on the borders.