While it’s impossible to say that any particular encryption method is 100% secure, PGP is generally regarded as being extremely safe. The two-key system, digital signatures, and the fact that PGP is open-source and has been heavily vetted by the public all contribute to its reputation as one of the best encryption protocols. Bruce Schneier once called PGP “the closest you’re likely to get to military-grade encryption,” and PGP.net says that there are “no practical weaknesses.”
Edward Snowden used PGP to send files to Glenn Greenwald when he broke the story that kicked off a lot of interest in encryption. And if it’s good enough for Snowden, it’s good enough for most—if not all—of the other people who need to encrypt things.