I am trying to make any white appear as transparent when I export an inkscape image as a pdf.

Here is the simple image I made:

I needed to use a white outline around each stick-figure, so when I overlap 5 of them they are all clearly discernible.

When I try to export this, the white outline I used is maintained and shows up when I have the image on a coloured background.

Hi.

You can either draw paths as they don't need any outlines or
to mask a black shape with an object made from your existing ones.

For the first, you would need to turn outlines to paths (Ctrl+Alt+C),
add a black fill with some transparency, and break the paths apart (Ctrl+Shift+K).
Then with subtracting some paths (Ctrl+-), you can have the desired parts, that you can combine together (Ctrl+K).

The easiest workaround would be adding a white fill to the paths and a black stroke colour,
grouping paths together, then using that group on a black object as a mask.