A total of 30 players were within two shots of the lead after the first round was completed at DiamondBack Golf Club.
Edwards made a visit to the chiropractor before the start of play and struggled through back pain for his share of the lead.
'I didn't know if I was going to finish, in fact I didn't know if I was going to start,' said Edwards, who was the last of the leaders to enter the clubhouse. 'After six or seven holes it was hurting pretty good but somehow I made it. Put it this way, if I would have been 5-over instead of 5-under I would have gone in, in a hurry'
Gump, who was the runner-up at The Players Championship in 1999, had only one blemish on his round, a double-bogey at the par-4 eighth. The 36-year-old collected seven birdies for his share of the lead.
'I've been playing well for about a year now and did reasonably well at this tournament last year,' said Gump, who has two Buy.Com Tour victories. 'When you drive in and see the list of players who have won this tournament it is quite impressive.'
A larger group was knotted at 4-under-par 67, including Derek Gillespie and Chris Wisler, winners on the 2002 Canadian Tour schedule.
The duo was joined by Mark Wilson, Tommy Biershenk, Victor Schwamkrug, Rob McKelvey, Scott Sterling, Jim McGovern, Dave Mackenzie, John Engler, Doug Barron, Kelly Gibson, Stiles Mitchell and Jason Bohn.
Cliff Kresge, who won the Buy.Com Virginia Beach Open in May, was among players tied for 20th at 3-under-par 68.
This is the second year that the Canadian PGA Championship is being played as part of the Buy.Com Tour. The tournament began in 1912 and is the second oldest golf championship in Canada.
Full-field scores from the Samsung Canadian PGA Championship