Here you can find some utilities that are helpful to prepare your text(s) for the processing by text analysis software.
A note on PDF-files: The file can contain texts that were generated by some text processing software like MS-Word, TeX/LaTeX, OpenOffice and the like. If you have this kind of PDF-files, you can extract the text and use it for later analyses.
Sometimes books or artices were scanned. Scanners store the information in graphic files - e.g. with file extensions like JPG, PNG or GIF. These files can be connected to a single file and stored in PDF-format. If this is the case, you cannot extract the text from this kind of files. You can try to use an OCR-software (OCR = optical character recognition) to do this, often scanners come with this software.