The bulk of the historical references in this post are based on Tolkien's Wikipedia page, so I may have various details wrong, but the broad strokes are likely accurate.

In July 1915, with considerable reluctance and after a great deal of pressure from relatives, 23-year-old John Tolkien enlisted in the British Army to fight in the Great War. One year later, he entered combat at the Battle of the Somme in France. Joining in the assault on the Schwaben Redoubt, he found himself under heavy German fire, and dove into a small natural dip in the ground for cover...

...and with a flash of light and a disorienting sense of motion, found himself rolling onto the street of a village in Andoran, in the year 4711 AR.

It's canon, thanks to Reign of Winter's Rasputin Must Die, that the "modern day" of Golarion roughly aligns with World War I on Earth. As a result, it occurred to me that it could be fun to play a WWI soldier who falls through an interplanetary portal and lands on Golarion, and a particularly fun version of that could be to play Lieutenant John Tolkien, and to bake in the implication that his legendarium of Middle-Earth was loosely inspired by his own adventures on Golarion once he returns to England. Here's how I would go about building that concept.

Stats: Dex and Int highest, Con and Wis good, Str and Cha bad. Tolkien was an academic and a philologist, so high Int is important, and Dex, Con, and Wis will be important for mechanical purposes. Str is unimportant, and Cha shouldn't be absolutely dumped since he was a talented storyteller and half-decent military officer, but it's not a priority at all.

Traits:

• Abject Belief: Tolkien was a devout Catholic in a time of strong anti-Catholic sentiment in England, and convinced his wife to convert, as well as playing a major role in C. S. Lewis's conversion from atheism to Christianity. Even in the world of clerics and gods that is Golarion, he may be able to hold on to his faith.

• Etymologist: If your GM is willing to waive the racial prerequisite, and if you substitute "English" for "Gnome" in the flavor, this trait is precisely on-brand for young J. R. R. Tolkien, who had invented or co-invented at least three conlangs and learned Esperanto by age twenty.

Feats: At level 1, Tolkien should of course have Skill Focus (Linguistics). Other feats to pick up over time include Esoteric Linguistics and Xenoglossy as he applies his passion for linguistics to the alien and often magical nature of languages on Golarion.

Languages: At start, you should speak English, French, German, and Esperanto. If your Int/Linguistics is high enough, you can also pick up Latin, Finnish, Greek, Welsh, or any of the other many languages Tolkien was familiar with in real life. Over time, you should also learn Common, obviously (unless your GM goes for the simplifying convention that Common is coincidentally identical to English), but also Elven, Dwarven, and Halfling--you can imply that Middle-Earth versions of those languages are based on the Golarion ones, and throw in an in-character comment about them resembling the real languages that the historical Tolkien based his conlangs on.

Class: This is the meat of the post. What class would Tolkien, not noted for his combat ability, be? There are a few options that lean into his storytelling abilities, but I'd go a different route.

He'll start as a Trench Fighter, of course; the archetype is from Rasputin Must Die and its explicit purpose is to represent soldiers in World War I. To make the build more mechanically palatable, you may want to take a one-level dip in vanilla Gunslinger for proficiency in firearms and Gunsmith. And that could be the extent of it, just play him as a Gunslinger 1 / Trench Fighter X and represent his intellectualism and curiosity through roleplay.

But I'd rather go a slightly more interesting route (one that makes use of his high Int, to boot). Tolkien was known for his academic pursuits and his imagination with regards to fantasy, so presented with the world of Golarion, it seems reasonable to say that he'd go for the most imaginative, fantastic academic pursuit: wizardry. So you multiclass into Wizard--I'd go vanilla Wizard, but if you go for Spellslinger you could drop the Gunslinger dip and make more use of his rifle.

From there you have two routes you could go. The one that probably suits the historical Tolkien better is to retrain your existing levels into Wizard, and then later level into the Loremaster prestige class to become a true academic. However, in actual play, I'd again go for a route that I think is slightly more interesting: keep the earlier levels. Go Gunslinger 1 / Trench Fighter 3 / Wizard 5 (or Trench Fighter 3 / Spellslinger 5), and then level into Eldritch Knight. At this point you've diverted significantly from the historical Tolkien, but not so far that there's not a foundation built from him, and a basis you can use for roleplay. Additionally, from there, you can function as a sort of Gandalf with a gun--Gandalf was more inclined to physical combat than magical attacks throughout much of the narrative, and you can adapt that slightly to using a rifle rather than a sword. If you wanted to have a little fun with it, you could even have him name the rifle Glamdring.

Overall, this could be a very fun premise to use as a base for your character in a serious campaign set on Golarion, or a gimmick for a sillier one-shot or mini-campaign; isekai and other fish-out-of-water stories always have the potential for a good time, and you can tie in League of Extraordinary Gentlemen-style romanticization/dramatization of the historical figure.