Upgrade Images to 300 DPI

I have a small batch of 1-5 images that need to be converted to a consistent, print-ready 300 DPI. Please upscale each file without introducing visible artefacts, colour shifts or over-sharpening—final artwork must look as clean as the originals, just crisper and suitable for high-resolution output... (Budget: $10 - $30 USD, Jobs: Adobe Photoshop, Affinity Photo, GIMP, Illustrator, Image Processing, Photo Editing, Photoshop, Photoshop Design)