It is software you install, on Windows or Mac, with matching apps for iPhone, iPad and Android and Linux builds on the same download page. It is not demanding — Wondershare's own install guide still lists a floor of around 512 MB of memory and 500 MB of disk space, which dates the page more than it describes the requirement. Any computer bought in the last decade will run it.
If you only want to try the AI, there is a browser version — PDFelement Online — that needs nothing installed. Its free tier currently allows a small daily number of uses of the PDF tools and a handful of AI uses in total, which is enough to find out whether the thing is useful to you before anything lands on your hard drive.
The desktop download doesn't expire, but it is a trial, not a free tier, and the limits are specific. Wondershare's trial-limits page currently states that converting a PDF to another format does half the pages — and at most three pages if the file is longer than ten; text recognition on scans stops at three pages; combining stops at three files; batch data extraction stops at two files; and compression and XFA form filling are switched off entirely. The AI panel gets around ten uses.
There are two shapes of paying for it. Wondershare currently sells a yearly subscription and a one-time perpetual licence, which costs more up front; both are priced per platform, with cross-platform costing more. Note that "single-platform" means one of Windows or Mac — not both, and not your phone. Discounts run on the store pages more or less permanently, so a crossed-out price is not a limited event.
AI use is metered separately from the licence. Plans include a limited number of AI uses; past that it is a separate add-on, sold monthly or yearly. Wondershare counts these as credits (the platform's unit of spend — each thing you make costs some), charged per use rather than per page, so a long document and a short one cost the same.