A4 Printout is underscale.

Hi all, just joined LibreCAD so I'm not only a complete newbie to this forum, but also CAD drawing. My head's getting a bit sore from banging it on the wall, so can anybody help me please with a print sizing issue. I've drawn a border & title block & when I try to print it in  A4 it's all undersize. For instance, the height's drawn at 200mm but the printout only measures 185mm. The scale in Currrent Drawing Preferences is set at 1, but as I'm unfamiliar with & don't completely understand the various settings, I'm not even sure if the scale is relevant in this case. I did read a few posts that said there was an incompatibility with Windows 10 Pro 64 bit operating systems sometimes. I've also tried printing while the print preview window is open, but to no avail. My system details are:

Version: 2.1.3
Compiler: GNU GCC 4.9.1
Compiled on: Sep 23 2016
Qt Version: 5.4.1
Boost Version: 1.60.0
System: Windows

Windows 10 Pro x64
HP Photosmart 7760 printer

Any suggestions on possible fixes or workarounds, & also any links to videos or informative sites on LibreCAD would be hugely appreciated.
Thanks in advance.

General Scale in Current Drawing Preferences only refers to the size of dimension elements like text and arrows.
The printing scale is set in Print Preview.
You also should tell your printer in it's windows driver settings to print at 100%, otherwise it might scale the print down to within the printable area. This might be your problem.
Have a look into the manual https://librecad.readthedocs.io/en/latest/index.html
Use the development version 2.2.0 rc3. It is stable and improved in many respects.

Thanks so much Dellus. I hadn't noticed the 'Scale' window & the three buttons which appear when I hit the 'Preview' button.  Strangely, the 'scale' was set at 1:1.08108 which when I changed it to 1:1, solved the scaling problem. Thanks also for the link to the manual.  
Keep safe.