Live KDP PDF Fix Tutorial

I have three paperback titles on Amazon KDP—a small written book plus two colouring books—built mainly in Canva with a few cover tweaks in Krea. After running the KDP calculator I exported everything as PDFs, but both the interiors and the covers are rejected for trim-size and bleed errors... (Budget: £10 - £20 GBP, Jobs: Adobe Acrobat, Adobe InDesign, Amazon Kindle, Canva, eBooks, Graphic Design, Interior Design, Print Design)