Firstly, I apologize for my poor English (I speak Portuguese - Brazil). I only know the basics, so I had to use a translator, but I hope I can help many who are facing the issue of not being able to run Mods with .pak files, just like I was.
I'll provide a step-by-step guide on what you should do, and I'll point out where I believe most people are making a mistake.
Download REUE4SS xinput: UE4SS-RE/RE-UE4SS (github.com) (file name: UE4SS_Xinput_v2.5.2.zip)
After downloading, extract the files to a location of your choice. There will be a folder with the same name mentioned above (UE4SS_Xinput_v2.5.2). Inside this folder, there should be the following files and folders:
Mods (folder)
Changelog.mod (file)
Readme.md (file)
UE4SS-settings.ini (file)
xinput1_3.dll (file)
Now, take all these files and folders, cut or copy them, and then paste them into the (Win64) folder. To get there, follow the steps below.
3.1. Open Steam -> Right-click on Palworld -> Manage (or Manage Files) -> Explore Local Files.
3.2. After opening the folder, navigate to: Pal\Binaries\Win64.
3.3. Inside Win64, you should place all the contents from the (UE4SS_Xinput_v2.5.2) folder mentioned in part 3.
Alternatively, to reach the (Win64) folder without opening Steam:
3.4. C:\Program Files (x86)\Steam\steamapps\common\Palworld\Pal\Binaries\Win64.
Now, with everything inside the (Win64) folder, look for the (UE4SS-settings.ini) file. If your system doesn't show file extensions, such as .ini, search for a YouTube video on how to enable file extension visibility on your respective operating system; it's straightforward. After finding this file, open it with Notepad, press CTRL + F, and type "bUseUObjectArrayCache" (without quotes). If you don't find it with CTRL + F, search for it manually. It probably has the value "true"; change it to "false," so it should look like "bUseUObjectArrayCache = false." Now, save and close this file.
Now comes the part that was causing me an error:
Inside the (Mods) folder, which after all this process you should have inside the (Win64) folder, I always deleted all the files in it and edited the mods.txt file, leaving it blank. But don't do that. In fact, make no changes except for one that I will mention below:
Open the mods.txt file. To get there, follow this path: C:\Program Files (x86)\Steam\steamapps\common\Palworld\Pal\Binaries\Win64\Mods/mods.txt. Edit the line "BPModLoaderMod : 0" and change it to "BPModLoaderMod : 1" (without quotes). After that, save and close it, and before installing any mods, run the game so that it makes all the necessary "configurations."
And within this Mods folder, you will always place mods with the extension ".lua." However, for ".pak" files, you should do the following:
Navigate to the following path: C:\Program Files (x86)\Steam\steamapps\common\Palworld\Pal\Content\Paks.
Inside the (Paks) folder, create a folder with the name requested by the mod creator. Some mods ask you to create a folder with the name "~mods," others "Mods," and the latest I've seen is "LogicMods." So, create it as requested by the mod author, and inside them, place the respective ".pak" file.
I tried to make this "tutorial" as detailed as possible.
Done! Now, just have fun!
I hope the translation into English is clear and understandable for you.