Spool file does not contain any text when PDF is printed

Question

When we print some PDF files via Adobe Reader, the printjob does not contain any text.
In Adobe Reader I can select the text but when you print it, it prints it as images (polygons records in EMF) instead of text (e.g. EMR_TEXTOUT).
Two questions:
How can we make sure that Adobe Reader always prints text?
On what is the decision based in Adobe Reader to print the PDF document as an image or as text?

Answer 1

Well we are looking for this information, otherwise we would not have asked this question. I really hope to get in contact with a Adobe Reader printing specialist who could give us these answers.
There must be something that decides to print as image or with text.
E.g. Adobe Reader 9 often prints text compared where Adobe Reader XI doesn't print the text for the same PDF.