Saved text in "Preview" unreadable

I have the following problem:

I open a pdf with the program "preview". I edit the document with the annotations toolbar (f.e. highlighting) and save the file. The next time when I open the file and copy a text from this document into another program, the text becomes unreadable and looks like this: ␣␣␣␣␣␣␣␣␣␣␣␣␣␣␣␣␣␣

What can I do fix that?
Thanks!

That is a multiple step process which is very lengthy and tedious, and you will need to create your own PDF to do it by copy/pasting it.

PDF Editor Pro on Mac App Store can edit PDF file with standard or OCR directly, and may well be of better use for you.

Mac App Store - PDF Editor Pro.

If you still want to explore the first option, heres where you can learn...

How to Edit PDFs With Preview in Mac OSX Leopard | eHow.com

I suspect it also works in post Leopard OSX's, if it doesn't... please let us know.

SM