Assuming that you're using a Windows PC, turn the printer on and put the document to be scanned under the lid. However DON'T press any buttons on the printer.
Go to your computer and click on the Start button to access the list of programs on it. Look under 'Canon Utilities' and you'll probably see something like 'IJ Scan Utility' listed there. (Canon sometimes change things though, so what you see might depend upon the printer model that you've got).
Open IJ Scan Utility. If your document is A4 size you don't need to alter anything, as that's the pre-set size for document scanning. If it's smaller thoigh, click 'Settings' and then 'Document scan'. Change the Paper Size setting to what it to what you want it to be and then click 'OK'.
Click the 'Document' button to start scanning the leaflet. Once the scan has completed, you'll then see 'Scan' and 'Cancel' buttons. If the leaflet has more than one page, move it in the scanner so that the second page is face down on the glass and click 'Scan'. Keep doing that until every page has been scanned. Once every page has been scanned, click 'Cancel'.
Unless you've changed the default setting, the scanned document will have ended up as a PDF file in your 'Documents' folder, with a long filename that's got the date in the middle of it. (e.g. looking at the scans in my own 'Documents' folder, I can see one called 850004393952-20210605-137013857520.pdf).
Go to wherever you send your emails from (whether that be a website or a dedicated email app) and create a new email to the person that you want to send the document to. Click the 'Attachment' button, which is often a paperclip icon. Navigate to 'Documents' and double-click on the long filename. Then, when you send your email, the leaflet will be attached to it in the form of a pdf document.