I had a go with the paid-for version and it was pretty much okay tbh, though I download GPX files rather than printing. You can get a pretty good idea of how it works from the free option – the main benefit of paid for, from vague memory, is that you get a bigger chunk of map to plan routes on.
As an aside, OS does great mapping, but is a commercial nightmare. I bet their digital customers – ViewRanger, MemoryMap, Satmap, Anquet etc – are delighted that OS having charged them loads of money for mapping data are now in the process of developing their own, effectively subsidised, mapping app which will compete directly with their own customers. What’s that all about?
Anyway, I’d give the freebie version a go, see whether you get on with the basics, and make a decision based on that.