Schematic file in PDF format, about 5.16 MB, titled BM62-64, which matches the naming of the Microchip BM62 and BM64 Bluetooth audio modules, likely a reference design or module documentation. No product or revision is stated. It helps when tracing module power pins, audio codec outputs, antenna connection and UART or control lines in speakers and headsets built on these modules. Open it with any PDF reader and confirm the module marking on your board before using pin assignments.
The button opens the matching file on RM Schematics, or a source page if it is not catalogued there yet. The original attachment is from @datasheets1. Enginerys does not host this file.
How to open a .pdf file
The standard format for schematics, block diagrams, power-sequence charts and service manuals.