Change PDF preferences in Preview on Mac
On your Mac, use PDF preferences in Preview to set the scaling of PDFs, choose how they appear when opened, change the kind of page numbering and add your name to annotations you make.
To change these preferences, choose Preview > Preferences, then click PDF.
Define 100% scale as
You can set how a document appears on screen or when printed by setting the scaling option. To display a document at full resolution of one image pixel equalling one screen pixel, click “1 point equals 1 screen pixel.” To set the print size of a document to be the size that appears on screen, click “Size on screen equals size on printout.”
On opening documents
To have documents that you opened previously, open at the last page you viewed, select “Start on the last viewed page.”
Opening for the first time
To set how documents appear when first opened, choose Continuous Scroll, Single Page or Two Pages from the “Show as” pop-up menu.
To set the page numbering in documents to display in Roman numerals, select “Use logical page numbers.”
To add your name to annotations that you make in a document, select “Add name to annotations,” then type your name in the field.