You can quote other file formats by simply opening them in SOLIDWORKS and clicking on "Add Part to Quote" for each.
If you're quoting an .STL file format, you will be prompted to browse to the folder containing the original .STL file.
Accepted file formats are: .stl, .step, .stp, .iges, .igs, .x_t, .x_b, .sldprt.
Maximum file size is 300MB.