How would ACAD render a high quality image to size 15"x10.25" at 300dpi?
From contributor M:
In paper space, set your paper size to whatever size you want from page setup manager. Draw viewport. Double click in it, size your object as you desire. Then render it. If you want really good results, AutoCAD does not have those capabilities. You can transfer your file in to VIZ or 3D Maxx and render it there.
As far as getting the image to size to 15” x 10.25” at 300dpi, unfortunately you will need to render to a file (preferably a .tiff for printing) and use an imaging program like Photoshop or Paint Shop Pro to change your dpi to 300 and resize the image to a printable size like you mention. This is because AutoCAD will render pixels only (e.g. 1600 x 1200) at a dpi of 72, so an imaging program is required to adjust to the format you are looking for.