The included setup file for ApowerCompress downloads the actual setup files and installs the software, which takes up ~175MB in the program's folder, with an ImageMagick folder added to Users\ [UserName]\ AppData\ Local\ & an Apowersoft folder added to Users\ [UserName]\ AppData\ Roaming\. The registry gets an uninstall key plus an Apowersoft key for the app. Given its long history of security vulnerabilities, the imagemagick code libraries *may* be cause for concern, but that's entirely up to you.
ApowerCompress reduces the size of PDF & image files... the primary way to make a PDF smaller is to increase the image compression [which lowers quality] *if* there are images in the PDF to begin with. The primary ways to reduce image file size is to reduce the number of pixels by making the image smaller, and to increase the amount of image compression, usually by setting the jpg compression level, e.g., P/Shop gives you 12 levels of jpg compression to choose from. The video option in ApowerCompress doesn't give you much to work with, so you might be better off using other tools to optionally reduce the number of pixels, using a smaller frame size, &/or using fewer frames, reducing the frame rate, &/or reducing the number of key frames, and of course using an efficient encoding format with the encoder set to a high level of compression. Some software will also let you encode video using multiple passes, which *might* reduce the file size slightly.