In AutoCAD LT, the easiest way to reload a referenced file (to see the results of changes made to that file) is through the External References Palette.
...or you can reload them all at once with the middle icon at the top of the palette.
Watch out for the "Refresh" option -- it's not the same as Reload. (As best I can tell, Refresh and Reload are similar to Redraw and Regen...close but not quite the same.) But once you've selected Reload all, the icon changes and becomes the default for the next time.
<edit> No sooner did I finish this than I found an old post that reminded me there's another way to reload drawing files: at the status bar. Right-click on the xref icon (marked below with a red arrow) and choose "Reload DWG xrefs." This one won't catch other types of references, but it's stll there.