Whether or not you can get a visa upon arrival depends on two things:
a) what type of visa (tourist or specific purpose visa), and
b) what country you are from
If you are moving to Bolivia and will be applying for residency, you have to come on the specific purpose visa. Most people cannot get this at the airport and must get it in their country of origin prior to traveling. Only a few countries are allowed to get one after arriving in Bolivia.
If you are touring Bolivia you would come on a tourist visa. The same pertains to tourist visas - some countries can get it on arrival, others must get one before traveling, and some countries don't even need one.
