Creating DLC

Konami has used DLC for years to serve as updates to PES. PES autists around the world have also used it to add content to the game that never would have been in it, thanks to things like licensing, money, and FIFA. Creating DLC is how you can modify the internal files of PES to turn this game into something spectacular. First things first though, you're going to need some tools.
==Exploring PES File Structure==
For your DLC to work, first and foremost, you have to understand how PES' files are set up. Files are stored in specific folders and must be named exactly as what they intend to overwrite if you want them to work. Locate the game data files, which are stored in "C:\Program Files (x86)\Konami\Pro Evolution Soccer 2017\data", and open the .cpk's using CRIFileSystem. Extract them to a folder of your choosing and start poking around to see what goes where. Most of the folders and files are named so that you have decent idea of what they hold / what they're for. 
If you want to look into specific things, here's a list of where certain things are held in PES' data files:
* dt15.cpk - Contains logos, flags, icons, and stadium preview images.
* dt30.cpk - Contains almost all stadium related files, including models, textures, billboards, and in-game staff. See Stadium Editing
* dt32.cpk - Contains player models.
* dt34.cpk - Contains kit textures and kit config files. See: Creating Kit Sets & Kit Managers
* dt36.cpk - Contains player face models, especially those of licensed players.
==Creating DLC==
In order to create DLC, you have to find out tell PES to write over the files that already exist in its data within itself. Start with an empty folder and name it whatever you want, bearing in mind that this will be the name of the DLC. In that folder, start building the skeleton of folders. For example, if you want to put in kits, you will continue to add folders until you are in the following location: "C:\DLCFolder\common\character0\model\character\uniform". From here, you would insert a "texture" folder to place the kit textures in, and a "team" folder to place the Kit Config files in.
From here, with all of your files properly named and in the correct spot, load up CRIFileSystem again. Drag the folder with your edited files into it and select "Build .cpk file". Let the program do its job, and you'll get a .cpk with the same name as the root folder of your DLC. Cut the new .cpk and paste it into "C:\Program Files (x86)\Konami\Pro Evolution Soccer 2017\download". PES won't load the DLC just by having it in the download folder though, you'll need to edit/create a file known as DPFileList. DPFileList is a .bin file that tells PES which .cpk's to load, and the easiest way to create one is with DPFileList Generator. 
When you first open up the Generator, you'll need to tell it where the DLCs are located as well as the path of DPFileList.bin (It's the same path, just for the second line add "\DPFileList.bin" to the end of it). There's an option just below that says "DLC:", select "No DLC" for that as we have no official PES DLC to work around. Now on the left side of the program, you will see a list of all the DLCs in your "download" folder. Simply check off what you want PES to load, they'll appear on the right side of the program. When you're ready click "Generate DPFileList.bin" and the file is ready. PES will now load every DLC you selected when it starts up.