FerociousCAD,
First let me welcome you to the group and thank you for the kind comment you made on YouTube on my "screen size" tutorial. It was well appreciated.
Now to answer your question.....
First, Go to the "dimension" tab to view the available options (icons, or toolbar buttons). Each of these available buttons allow you to place dimension lines on any lines in your drawing, however, the icon must be chosen based upon the orientation of these lines, arcs, and circles that you want to dimension. In other words, if you wish to draw a dimensional line to show the length of a horizontal line you MUST choose the "draw a horizontal dimension" button for this task as no other button is capable of performing this task. The best way to learn the role of each button is to first SELECT THE BUTTON, then press "F1". When "F1" is pressed a short explanation and drawing will appear to help you understand it clearer. "F1" will work with all other toolbar buttons as well, so dont be afraid to use it often as it is a great help to those just starting out.
One more thing....
If you look at the bottom left of the screen while you are using Deltacad
you will find that it will give you a short summary on how to use the current function you are using, "F1" simply expands the help on that function.
Hope this helps!
Chris "i44troll"
"......How can I measure line length without have to draw a parallel line next to the original?........"
Alternatively you can open the "edit" tab and choose the "edit object data" button (Deltacad chooses that button by default), select the line you want to know the length of and read the dialog box that pops up. It will tell you EVERYTHING about that line and give you the ability to make changes to it as well.
Chris