Datasheet for the Microchip PIC16C505, a small 14-pin microcontroller from the baseline PIC range, provided as a 1.18 MB PDF. It covers pin functions, oscillator options including the internal RC, configuration word, instruction set and electrical characteristics. The document helps when tracing a board built around this controller, verifying the supply and reset pins and confirming a replacement part. Being a C-series device, it is usually one-time programmable, so repair means fitting a correctly programmed chip rather than reflashing in place.
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 @datasheet. 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.