Be careful as that booklet is outdated and hence why it's not available on immigration's website anymore.
The 300 website IS up to date and contains the answer you seek. When applying online, you color scan original documents and they do not need to be certified.
Certified copies of documents were for paper applications only because you wouldn't send in you passport or birth certificate or anything else as original documents. Therefore you needed to get copies that were certified as true copies of originals. Paper applications also needed to send in the original police checks, whereas this also does not apply to online apps. You just scan and upload police checks.