Searching double keywords

When you try to search for more than 1 word in the document viewer, the result gets unpredictable and mostly does not work.

So let's say a document has 100 times the term: John
Searching for this works

It has 10 times the combination: John Smith
Most of the times you can get to the first result, but then it stops.

Is there anything I can do to fix this?
