Combined Microchip datasheet for the PIC18F2220, PIC18F2320, PIC18F4220 and PIC18F4320 flash microcontrollers, provided as a 7.14 MB PDF. The 22xx and 23xx parts are 28-pin devices while the 42xx and 43xx come in 40 and 44 pin packages, differing mainly in memory size. Use it for pin assignments, oscillator and configuration settings, and electrical limits. When probing or reprogramming via ICSP, confirm the exact part and package, since signals sit on different pins across variants.
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.