Here you can find tools to edit game data files such as WADs and PK3s.
Perhaps the 3 most known WAD editors to date are XWE, SLumpEd, and SLADE 3. The former two were lump editors of the past generation, while SLADE 3 has superseded both XWE and SlumpEd.
A WAD file, short for Where's All the Data?, is the original type of data file used when Doom was first created. Pioneered by ID software, WAD files hold sprites, sounds, musics, graphics, textures, patches, and basically all other resources needed for a WAD. WAD files are usually recommended to learn before taking on a PK3, simply because WAD files are much easier to learn to edit.
PK3s, on the other hand, are ZIP format files, that use a similar structure to WADs. The main advantages are that they are compressable, meaning they can be smaller than WADs, and that they more organized: everything goes in individual directories.
SLADE 3 is the latest and greatest WAD and PK3 editor currently available. This successor to SLumpEd has a multitude of features. It supports Zandronum's custom data, and supports advanced features. It has full support for all ZDoom and Zandronum supported palettes, image files, music files, and so on. It provides an easy interface for manipulating data, such as converting graphics, sounds, modifying texture offsets, editing code, and so on. It also includes a work-in-progress map editor.
For more information, visit the SLADE website.
The predecessor of SLADE 3, this editor offered a multitude of features. It allowed users to edit or create WAD and PK3 files. It recognized many new Zandronum features, and it had full PNG support for files.
For more information, visit the SLumpEd website.
eXtendable Wad Editor (XWE)
Once the superior WAD editor program, this editor was eventually discontinued. It only supports the editing and creation of WAD files; PK3 files are not supported in this editor. XWE has been praised for its simple approach to adding PNAMES and TEXTURES to WAD files. However, XWE often has problems with .PNG files and has been known to corrupt WADs if another program uses the same WAD that XWE has open, as it reads and writes to the WAD at run-time and does not adapt to changes. The program is generally unstable on newer systems and using SLADE 3 is recommended.
For more information, visit the XWE website.