There are more than 75,000 species on the Pan-species Listing (PSL), but if you'd really like to download this for any reason it's easy to do! Just go to the checklist and click on the green download button on the right side.

Probably more useful is that you can download just a taxa group rather than the entire checklist, so just the Orchids, or all the Vascular Plants, for example.

Note that you can also download your own species or family lists, or your targets or blockers, or indeed download from any other person's list. Just look for the green download button again when you are viewing the list you wish to download.