After watching this great tutorial by Andrew Price Quick Tip: Import Textures Like a Boss | Blender Guru I got an idea. What if I use that method to load blueprints!
It works great!
Go to File -> User Preferences -> Add-ons -> from the Categories menu -> Import, Export and then find add-on called "Import Images as Planes" and check the box. Then Save as Default. See 1st attachment picture.
Go to File -> Import -> Images as Planes. Search your blueprint and see it apparear into the top view, with automatically correct plane sizes etc... COOL! Now the plane seems to be white but hit Alt+Z and the texture will be shown in 3D viewport. See 2nd picture
Now there´s a problem. If you select viewport shading as Solid-mode to start modeling, the texture will disapparer. Fix that by pressing N and from the Display menu find and check "Textured Solid". See 3rd pic.
Oh and if your plane is textured from the both sides, which makes seeing the front or back blueprint impossible. Go to Edit mode, select all faces (A), go to Object Data panel, find a Texture Face drop down meny and uncheck "Two-Side". Repeat that for every blueprint plane! See 4th pic.!
Happy modeling! I hope this little tutorial makes adding blueprints alot easyer and most important - faster!