[Twinge]

I would avoid using jpeg as much as possible though - jpeg files are lossy, which means they lose image data when you save them (even high resolution). If you're saving something you're working on in a raster (non-vector) format, you should use a lossless format (one that does notlose any image data) such as PNG or TIFF.

 

[Twinge]

If the resolution is high enough (e.g. 300dpi), I think many printers will still accept it without additional charge. Of course, this WILL vary from printer to printer, so make sure you know what your printer needs before making the artwork. Or, conversely, find a printer than can print your already make artwork without extra fees

 

[Twinge]

Your printer specifically uses jpeg?? That sounds really odd. Standard raster formats for this sort of printing are going to be ones where there is no loss of data - tiff for example, or program-specific ones like psd. A jpeg saved at high quality will probably not look much different, but there is really no reason for a printer not to be able to accept at least some form of lossless file format. Personally I like png, as it'll give the smallest file sizes for raster-based lossless generally.

Most imaging programs do let you save as a variety of formats, but a handy program you might still check out is Irfanview. This freeware program can convert between tons of different formats, lets you adjust jpeg quality with saving, and does a few other useful things.