Although it is recommended to follow Step 1, not doing so will result in a bunch of errors but those will be temporary. As it has always been the case when upgrading to a newer version of TextMesh Pro, you have to remove the previous version first by deleting the "TextMesh Pro" folder. As usual be sure to backup your project first and any files or assets you may have saved inside the "TextMesh Pro" folder. Once the previous version has been removed, then import the package version. If you imported the package version of TextMesh Pro prior to having removed the previous version, you'll get more errors but again these will be temporary until you remove the previous version. This may also require that you restart Unity as most likely to old DLL will have been loaded and cannot be unloaded without a restart. Again, these errors and wonky state is temporary. Once you have removed the old version, installed the package version and potentially restarted Unity, all these errors should be gone. You will then need to convert the project files to the new format using the "Project Files GUID Remapping tool". Upgrading from the older versions to the package manager version can be scary but once on the new package manager version, future updates will be much simpler as it will no longer require removing the old version first. Update Just tried again going from previous DLL version of TMP and importing without closing any open scene and without removing the previous version of TMP first and although you will get lots of errors. Once the previous version is removed and Unity restarted (which is required because the old dlls have been loaded), all errors went away and besides having to convert the project files, it all worked fine.