You can use this free tool to do PDF Magazine Flip, then add to Squarespace via Code Block. Follow these steps.
#1. Access this free tool and setup.
You can setup by uploading your pdf file or using the pdf link.
You can setup color, fonts… here
You will have
#2. When you’ve done everything, click Add to Website for free
Next, click Publish
Choose FREE plan then copy Embed code.
#3. Edit Page (Squarespace) where you want to place this pdf magazine flip > Add a Code Block
Paste embed code you have in #2 to Code Block.
#4. Save. Preview the page to see the result.