GerbMagic is a free viewer for Gerber RS-274x and Protel ASCII PCB (Protel v2.5 to v2.8 formats). It can also convert Gerber RS-274x and Protel ASCII PCB to PostScript, PDF, TIFF, BMP and RID formats.
If you have an image setter which supports either PDF, PostScript, TIFF, BMP or RID, you can plot Gerber and Protel PCB files with the help of GerbMagic.
GerbMagic is a fast, high resolution software RIP (Raster Image Processor) for RS-274x and Protel ASCII PCB. Up to 30,000 DPI has been tested with excellent performance. Multiple Gerber and PCB files may be grouped onto a single page in WYSIWYG (what you see is what you get) fashion.