Microsoft Office's Word, has a capability called "Outline". This suite fully implements this. Some other office suites may claim that they have this, but really it is an [extremely] limited form of it. BTW, for the free version an unobtrusive small ad pops up no more than once a day.
ProGood free version
ProExcellent Microsoft Office compatibility
StudiousDaichinTengri (140 karma) recommendsPDF-XChange Editor Plus
Yes, I do use it to manage my documents. It has Tags, great storage and great search options, so yes !
ProBest web clipper
ProEvernote is synchronized
ProPremium allows search in attached files and documents
ProEasy to use
ProConsolidates all your information
ProPowerful features for organising your notes