Whilst not all poster assignments require you to have a copy or your work printed to full A1 or A0 size for submissions, it is still important that the printed work you DO submit is of high quality.
If you do need to have your poster printed in a size larger than A3, you'll need to send your work off to be printed professionally. Before you do so, however, it is a good idea to create a PDF version of your poster that other computer platforms can open, view and print.
Finding a printer
If your institution does not have a copy or print shop, many local print shops offer services for poster printing. You may also find print shops online that can accommodate your printing needs. The cost of having your poster printed will depend on the size, colour and additional services (such as laminating and proofreading) required.
Be aware that print shops are not responsible for proofreading your work (unless offered as an additional service), therefore, you must review your work before sending it. Also, keep in mind that colour appearance on a computer monitor and in print may vary slightly. Make sure you allow enough time for your poster to be printed- this can take from 2 days to 2 weeks, so don't leave the printing to the last minute.
Image available CC-BY-NC-ND from Flickr