That's my problem folks. I have to do a language work, and I can't copy text, without removing every accents.
I assumed that your problem appears when running pdflatex on a document containing special characters from Spanish and copying from the resulting PDF file to another file.
In this case, to prevent the problem, simply use the Cork encoding: add in the preamble
If you don't do this, then special characters (accented vowels, the tilde in the "ñ" and the crema, in Spanish) won't be copyable from the obtained PDF document.