Most of the IRCC Forms are created in a way on which you can not do signature digitally or embed your signature (as an image) into the PDF. Even if you purchase Adobe Acrobar Pro DC for 14 Canadian dollars - you will not be able to do it. But there is a way I just happen to find.
Open the IRCC Application Form. (Example PRTD PDF Form:
https://www.canada.ca/content/dam/ircc/migration/ircc/english/pdf/kits/forms/imm5524e.pdf). Save the form on our computer first and then open it with Adobe Reader DC. After you fill up the form you click on the "Print Form" button which can be found on top of each page. From the Print Dialog Box -> Choose Printer as "Microsof XPS Document Writer" and click on "Print" button. The system will ask you to save the file in OXPS format. Just save the file in any folder in your machine.
Now, go to that folder and right-click on the .oxps file you just created. You should see an option called "Convert to Adobe PDF". You can select this option to save the file in PDF format now. After you successfully created the PDF file.
Hope this helps!