You will find countless low-quality scans on random blogs. Avoid those. Here are the three reliable sources for professional-grade orchestral excerpt PDFs:
The compiled Orchester Probespiel book is under copyright (Schott, typically published 2000 or later). Downloading a full PDF from file-sharing sites is copyright infringement. Many of the individual orchestral works (e.g., Beethoven, Mozart) are public domain, but the selection, editing, and bowings/fingerings in the Probespiel edition are protected. Orchester Probespiel Cello Pdf Download
While compiling your own excerpts from IMSLP is possible, the Orchester Probespiel saves months of preparation. It provides: You will find countless low-quality scans on random blogs