I'm having trouble printing and scaling with LibreOffice CAD 2.0.7 under Mac OS X 10.10.3. At first my print was roughly 65 mm square in the lower left of a US letter page. More recently, the page prints all white -- and "Export as PDF" is the same.
Specifically, I downloaded "http://www.atriumsretirement.com/largefloorplans/The%20Elms.gif" and successfully placed that as a layer "gif" of a new drawing using "insert image". Then I successfully traced some of the lines in a new "outline" layer, in which I set line width = 0.13 mm (ISO) with color = dark green. These look fine on the screen but print as described above.
I saved the project as "Elms2015-06-04b.dxf" then brought it into LibreOffice 188.8.131.52. This displayed the lines I had drawn but not the image I had drawn from. Moreover, I had set the line as solid and dark green; from LO it printed as dashed lines in a very pale, barely visible light green. The size and placement of the drawing were better but still not what I wanted: 50% larger in LO than from LC and in the center of the page (vs. lower left in LC).
In addition to failing with various print, print preview and "Export as PDF" options, I also failed when trying Modify -> Scale.
Have you already asked for help some time ago? I darkly remember I had to deal with some "Elms" floorplan drawing once.
First you have to set up the page properly. Then, when importing the gif, the problem is you don't know what scale and what dpi it is. So trial and error. What scale do you want your drawing to be?
I have provided a sample, a template for inch and scale 1/96 I have made a while ago, and inserted the gif from your link with setting factor 1, dpi 1. By chance it looks ok. Now you have to know the real length of something in the gif, like a door opening, length of a room, the bathtub or whatever, and scale the gif to the proper size. After scaling it will seem disappeared, doing an "autozoom" brings it back.
Put your "The Elms.gif" into the same folder as my dxf and try out. Use Print Preview in any case. Type in the scale 1/96 manually, it's not offered, and center the drawing on the page.
LibreOffice can import dxf, but can't do all the features, the geometrics might be right but the layout will be spoilt.