Poster Editing and Resolution Enhancement

I need assistance with a poster I've designed in PNG format. The poster is 36 in x 72 in. The required edits are minimal: adding a QR code and a logo. However, I need the resolution significantly improved for print quality and prefer for it to be editable... (Budget: $10 - $30 USD, Jobs: Digital Design, Graphic Design, Illustrator, Image Processing, Image Upscaling, Photo Editing, Photoshop, Poster Design, Powerpoint, Visual Design)