When you complete the return, you will have to click on Netfile and receive a confirmation number that the return has been filed successfully and received by CRA. You did not indicate in your question that you have a confirmation number.
If you cannot Netfile for any reason, you would be able to print the PDF forms without a watermark on the papers and you personally have to mail it to CRA to one of the addresses in this link: https://www.canada.ca/en/revenue-agency/corporate/contact-information/where-mail-your-paper-t1-retur...
If you are not sure whether or not CRA has received your return, please contact them 1800-959-8281
Or check your "My Account" status: https://www.canada.ca/en/revenue-agency/services/e-services/e-services-individuals/account-individua...
I hope this was helpful
