command line language for Android tablet (wget equivalent)
Did you tried Termux?
The terminal emulator for android, this does not require any root access either.



Edit: to install wget type pkg install wget and press enter.

For pdf viewer use native android one such as Mu Pdf or, Google pdf viewer

Once installed you can try xdg-open filename.pdf
It will give you a list of the compatible app to open the file or else you can open the pdf viewer app to browse files of your choice.