Czech letters in Adobe Acrobat

I am working on a document which is partly in Czech, it is a PDF (not originally cerated by me) and my problem is that most of the Czech letter with special symbols are not recognized as letters.The excisting special letters are overwritten by other letters. Also when I copy and paste a correct Czech word, from a Word or other document, Adobe Acrobat will leave out the letters with special symbols and paste only half the word.
I tried setting the language settings to Czech but this unfortunately doesn't work. Anyone experience with this?