Concerning the 2SC5452, this 42.4 KB PDF is listed as a schematic but, judging by size and part number, is a component datasheet for an NPN transistor in the Japanese 2SC series. It should include the maximum ratings, electrical characteristics and mechanical outline. Technicians use it to identify pins for diode-mode testing and to choose replacements. Confirm the marking code on the device and compare it with the sibling 2SC5450, 2SC5451 and 2SC5453 sheets when looking for close equivalents.
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 @cyberlanelectonik. 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.