scanning to PDF

Hi. I'm trying to scan a multi-page document to PDF. I go in to system preferences and print and scan. Open up the scan utility. Voiceover shows a button that says show details, I hit it, and it comes up with all the settings, where to save the file, file name etc, etc. I go to the popup box that says format and change from JPEG to PDF, and also hit the checkbox that says multiple pages. Problem is I then go to the scan button press ctrl option space and nothing happens. It only works after I hit the hide details button. But then it reverts to scanning to a single page JPEG. I feel like I'm missing a step or maybe Voiceover doesn't read all of the scanning screen? Can anyone help please? I really need to get this document scanned and emailed ASAP. I'm not bothered about OCR, just need a PDF. I'm using an epsom scanner with mac Sierra. I've had this issue before but can't remember how I fixed it.
Thanks..