A1 Poster High-Res PDF Conversion

I have a single PDF that was set up at low resolution and now needs to be printed at A1 size (594 × 841 mm). The file looks fine on screen but will pixelate badly if sent to press in its current state, so I need it rebuilt or up-scaled into a crisp, print-ready PDF... (Budget: $10 - $30 AUD, Jobs: Adobe Illustrator, Adobe InDesign, Adobe Photoshop, Graphic Design, Illustrator, Photoshop, Print Design, Vectorization)