Portugal is a fabulous place for walks. 
There is such a wide variety of landscapes from beautiful beaches to scrub forests, from cultivated river valleys and lagoons to mountain ranges. And it isn’t difficult to find a walk as there are so many public tracks and paths. However the downside of all these tracks is that without a map you can end up taking too many detours!
Most of us these days use our phones, sat navs or print outs of digital maps to get from A to B, and generally these work fine. However if you are planning to walk then nothing beats a proper map. And the best ones in Portugal are printed by Instituto Geográfico do Exército. We have purchased quite a few of their 1:25000 series and strongly recommend them for anyone living here or intending to regularly walk in Portugal. They also produce good driving maps so take a look.
If you are not sure where you want to walk just yet though or perhaps you are only here for a short holiday, then you’ll probably prefer to download a guide/map for individual walks. And the good news is you can do this!
For every signposted hiking trail in Portugal check out Walking Portugal. From here you can search by region and town, and then download for free a small pamphlet for every walk. It isn’t the most user friendly of sites but it is really useful for discovering new walks. I’ve used it quite a bit. The pamphlets I admit are a bit hit and miss, which can be a problem if the signs have been moved by hunters or damaged by the elements. We haven’t got lost yet but have had a few moments of “hmm, where do we go now”!
Another site I have recently discovered is ‘Walks in Portugal‘. They provide hiking pamphlets which you can download for a minimal fee and also sell hiking maps. They even provide an accommodation service for two long distance trails, so well worth visiting their site if you enjoy hiking.