Which one of the following is correct?
1. Veronica traveled all over the world in 2007.
2. Veronica had traveled all over the world in 2007.
The correct answer is no.1.
On the GMAT use past perfect tense only when you want to clearly show that some event happened before another event in the past and had an impact on the event in the past. e.g. If you say "Veronica had travelled all over the world by 2007" it is correct, because 2007 is the simple past and before 2007 she travelled the whole world, which you write in past perfect tense. So you are saying that she started travelling the world before 2007 and had finished by 2007. Whereas the first sentence means that she travelled the whole world in that particular year (2007) only.
Again if the sequence of events is obvious then don't use past perfect, e.g. x happened before y, or x happened after y.
Hope I've been able to answer your question!
Kudos are motivating!