The writer I’m discussing is Jason Bulmahn, creator of Pathfinder and its current Director of Game Design for Paizo. Bulmahn writes parts of instruction manuals and adventure paths for tabletop RPGs. Jason acquired a ton of experience before he began designing Pathfinder, playing TTRPGs like Dungeons & Dragons throughout his life. His experience eventually got him a job writing scenarios for the Living Greyhawk Campaign run by Wizards of the Coast, where players across the nation meet in small groups to play Dungeons & Dragons in one vastly interconnected fantasy world. He later moved to Paizo Inc. and worked on Dragon Magazine until the end of its print run, after which he and the rest of Paizo focused on creating their line of game mastery products and Adventure Paths for D&D 3.5 Edition. Two problems arose as Wizards of the Coast prepared to launch D&D 4th Edition: 1) Paizo was unable to obtain the 4th edition rules early, meaning they couldn’t design Adventure Paths until after the game had been released, and 2) Paizo wasn’t sure how the new content license would work, meaning they might have to shift their approach if they wanted to continue profiting off of D&D-based books and materials.
During this time of uncertainty for Paizo, Bulmahn had been independently working on his own edition of D&D. Instead of designing a major overhaul like Wizards of the Coast had done with D&D 4th Edition, his initial idea was a “D&D 3.75.” His idea was to take the core ideas of D&D 3.5 and make various adjustments and improvements, presumably based on both his own opinions and common community feedback. In his initial writing, Bulmahn was mostly analyzing the existing D&D 3.5 rules, identifying their strengths and flaws, and using his own experience in the game industry to make them better (more entertaining, more steamlined, etc.). It’s also likely that he took a lot of inspiration from his experience playing other games: In his YouTube video on how to get into the games industry, he stresses the importance of playing a variety of games (games you love, games you hate, video games, board games, games in different genres, etc.) and analyzing those games – their strengths, their weaknesses, and why certain decisions were made by the designers. It seems that both this research and Bulmahn’s vast experience with D&D granted him the expertise to design a great new edition.
As Paizo was brainstorming what to do about D&D 4th Edition, Bulmahn pitched his D&D 3.75 as a standalone set of rules that Paizo could publish. Paizo loved it and within a week, Bulmahn was the lead designer for the newly coined Pathfinder RPG. Pathfinder has been Paizo’s focus for the past decade, even releasing a sci-fi variant (Starfinder) and currently gearing up to release Pathfinder 2nd edition.
Bulmahn is now the Director of Game Design at Paizo and Team Leader for Pathfinder 2E. Though he presumably still does plenty of work establishing the design direction for the game, plenty of his writing nowadays involves addressing questions and feedback from the community. Looking through his posts on the Paizo forum, there’s various posts introducing new content, explaining the thought process behind certain changes, and otherwise moderating discussion about the game. It’s unclear exactly how much of his writing is published in new Pathfinder books, but he does mention editing the Chapter 1 text for a Pathfinder 2E book in this post.
Note from this post that Bulmahn directly incorporates feedback from the community into his writing. Although Bulmahn, being the head of game design, has a lot of freedom with incorporating his ideas into the game, he’s still ultimately held accountable by the community. For example, Paizo released a Pathfinder 2E playtest a while ago (basically an open beta) and a lot of the community was unhappy with the Resonance system included in the rules. (If I remember correctly, Resonance made Charisma and Use Magic Device less weak but placed too many restrictions on magic item usage). Paizo recently ended up scrapping the entire Resonance system due to its unpopularity. I’m sure Bulmahn gets feedback from other writers on his idea, but it seems like the main barrier between getting his ideas published is community feedback.
It’s not entirely clear exactly how Bulmahn gets paid, but, given his roles in management and communication with the community at Paizo, he probably gets paid a regular salary for all his various work. Likewise, it’s unclear exactly how his writing process goes, but it seems to be a mix of analyzing existing rules, editing issues, and making improvements.