If you need to install PDF2XL silently, this can be done using a command line console.
Open your preferred command line console (cmd / powershell) in administrator mode, then run the following command:
msiexec /i pdf2xl.msi /qn
After a few seconds, you will be able to invoke PDF2XL from the Start Menu and Desktop.
This form of installation will always be per-machine (to the default Program Files folder), so it is required for an administrator to invoke the command.
If a per-user (or non-admin) installation is required, then run the following command:
msiexec /i pdf2xl.msi /qn ALLUSERS="2" MSIINSTALLPERUSER="1"
This will install PDF2XL in the %LOCALAPPDATA%\Programs folder of the current logged in user.
Up until version 8.3 (included) the quiet installation will open a browser "Thank You" page when finished.
The per-machine installation folder can be changed by appending TARGETDIR="c:\destination" to the command.