A package is a namespace that organizes a set of related classes and interfaces. Conceptually you can think of packages as being similar to different folders on your computer. You might keep HTML pages in one folder, images in another, and scripts or applications in yet another.
If you want to do a specific kind of automation or programming, then you have to download or use those packages to do that automation.
Now, the PDF package has successfully installed in your workflow, go to activities and search for PDF-related activities, you will find all the PDF-related activities downloaded as a part of the PDF package.
To Uninstall a package, go to manage packages, you will find a PDF package. Once you click on the PDF package, it will navigate to the UiPath.PDF.Activities wizard, Click on Uninstall
Now, go back to the activities pane and search for PDF-related activities, you won't find any PDF-related activities here.
In the same way, we can install multiple packages at a time.