Variable Pig issues are A4 PDFs with a divisible-by-four page count, ideal for printing the zine as an A5 booklet (2 pages on each side of each sheet). Whether or not your printer natively supports booklet mode, you can do this using the free Acrobat Reader DC program.
Follow the instructions for Reader X
See also the screenshot below:
Note that Acrobat Reader downscales the print size slighlty (about 96%) in booklet mode.
It is possible to booklet print from your browser, but only if your printer supports it natively - for example in Chrome click on "print using system dialog" as shown below.
Pretty straightforward to choose just the page(s) you want in the dialog.
There are a couple of scaling issues with Acrobat: