Do not just search for files; search for communities. The following groups were active goldmines in 2021 (verify they still exist by pasting these URLs into VK):
Not strictly PDFs, but many VK pages in 2021 offered ZIP files containing 10,000+ Guitar Pro tabs. These allow you to play along with animated tabulature on your computer. guitar books tabs vkcom 2021
The 2021 Era: In 2021, VK was a primary hub for sharing guitar literature due to easy access and less aggressive DMCA takedowns compared to Western hosting sites. Many Western users discovered VK through "bridge" sites or forums that linked to specific VK posts to bypass paywalls found on other tab sites. Do not just search for files; search for communities
Current Viability: