Hello Daniela, I just joined this team and found that no one replied to your question which was posted last year ! OMG!
anyway, will put my answer just in case someone else gets this problem.
You will need a program that opens eps file, most popular one is adobe illustrator , so you open your PDF file using adobe illustrator then you save as it as eps, that is it ! now it is eps again. simple :)
Reason the eps file you get is exactly as original because the PDF file you have was created from an eps file, so it also vector and can be changed simply by saving it as eps using adobe illustrator.
x