MacBook Pro mid 2012 memory upgrade

Only if it is not a retina display. See OWC or Crucial for compatible RAM.

The Non-Retina Model can be upgraded to 16gB of RAM. The Retina Model can not be upgraded after purchase.

If this is your MBP

https://everymac.com/systems/apple/macbook_pro/specs/macbook-pro-core-i7-2.7-15-mid-2012-unibody-usb3-specs.html

Yes, you can upgrade to 16 GB.

Supports 1600 MHz PC3-12800 DDR3L SDRAM SO-DIMMs (204-pin).

Macs are fussy about RAM. Both Crucial and OWC are reliable vendors with high quality RAM.