Lets see, meanings for the word 'Trekker';
1. One who treks; thus, a hiker [from dictionary]
2. A traveler (a person who changes location) [from dictionary] (Note: First two are all pretty similar!)
3. AnavidfanofStarTreksciencefiction,televisionshows,andfilms;byextension,apersoninterestedinspacetravel (also known as a Trekkie) [considerable disagreement among Star Trek fans over whether to use the term Trekkie or Trekker]
And it now also means;
4. A great new freeware software by GratSoft.com that lets you trek (that is to move) through your PDF files. Trekker lets you view, print, split and join pdf files, It also lets you extract text from your PDF pages. You don't need to leave Trekker to view the other pdf files as it includes its own file explorer like sidebar. New upcoming features for Trekker will include the ability to view image files and to add them to your PDF files. Visit the project page for more details.