In Pages, Export your file as a pdf (Share>Export>PDF). Then open the Automator (Applications folder) select a custom workflow a and set up as below
"Get Specific Finder Item" is under Files and Folders, then click add and navigate to your saved pdf.
"PDF to Image" is under PDFs, select the folder to save to and if you want a custom name, otherwise it will name as "Original File Name-page#"
Then click Run in the upper right hand corner.