If you find a "free PDF" online, check if it is missing the answer key or audio files—many illegal scans omit these.
Endstation C1 lists Redemittel (speaking phrases) for each chapter. endstation c1 pdf
Modern learners often study on tablets or laptops. A PDF linked to local audio files (if acquired legally) allows for seamless navigation—clicking a QR code or hyperlink to replay a difficult listening comprehension track, which is clunkier with a physical CD. If you find a "free PDF" online, check