Before you search for a PDF, you must understand the target. A standard British brass band consists of 25–30 players plus percussion, with a specific instrumentation:
The Bass Trombone is the only brass instrument traditionally written in bass clef at concert pitch . Arranging Principles Scoring for Beginners scoring and arranging for brass band pdf
For a comprehensive deep-dive, the following authoritative guides are recommended: An introduction to: Brass Bands | Making Music Before you search for a PDF, you must understand the target