If mirrored printing is not offered in your printer's driver, there's a pretty simple way to do this. It does require the use of some additional software, but the results are quite acceptable. The additional software that I use is
HardCopy and
IrfanView. I prefer the method below as it gives me clean monochrome prints rather than the grey tones that are produced directly from ExpressPCB.
Here's the procedure:
1. Start out by marquee-selecting the entire PCB -- including the "edge" frame of the board. This has the effect of changing the colors displayed, makning the traces grey.
2. Then, using a slective capture utility like HardCopy, capture an area slightly larger than the PCB, saving it to disk, preferably as a .BMP file.
3. Open IrfanView, and make sure that the
View > Display Options setting is set to
"Do not fit anything".
4. Open the captured .BMP image in IrfanView.
5. Do an
Image > Decrease color depth and set the image to
"2 colors (Black/White)".
6. Now do an
Image > Horizontal Flip.
7. Print the image without doing any scaling.
8. Measure the printed image, using the PCB "edge" lines.
If the image is scaled correctly, you're done. If not, calculate the scaling percentage based upon the actual printed size and the expected size. In IrfanView, scale the image accordingly, reprint it, and repeat the measurement process. Note that the printed size, and therefore the scale factor will likely change from one printer to the next, and, depending upon the accuracy of your printer, scaling may not be necessary at all.