To travel to Canada you may need a visa or an Electronic Travel Authorization (ETA). The following tool can help you determine the entry requirements and help you apply: http://www.cic.gc.ca/english/visit/visas.asp.
The Association for Computing Machinery (ACM) is able to provide visa support letters to attendees as well as authors with accepted papers, posters, or members of the conference committee. Note that ACM does not issue formal invitation letters for visas to attend ACM sponsored conferences.
For visa support letters, refer all requests to firstname.lastname@example.org. Please allow up to 10 business days to receive a letter. All requests are handled in the order they are received. The information below should be included with the request: