For what it's worth, Preview is a relatively thin shell around Apple's own PDFKit: https://developer.apple.com/documentation/pdfkit https://developer.apple.com

For what it's worth, Preview is a relatively thin shell around Apple's own PDFKit: https://developer.apple.com/documentation/pdfkit https://developer.apple.com/documentation/pdfkit Whether that could itself be open-sourced is an interesting question. (My concern would be that parts of it might be covered by Adobe NDAs.)