How to Add Interactivity to an Existing PDF for an eJournal or eBook

[smart_reliability5CBE]

Hello everyone, hope you're well ! 

I'm a beginner with adobe. I've created a fillable journal, i've already print the product and made my first sales, i've already finished the pdf on Canva, and I wanted to add an ebook / ejournal option so the client could fill it out on their device. so I was wondering how to edit a document that already exists.
Thanks in advance!

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[BobLevine]

You don't mention InDesign at all in your question so I'm not sure what you're hoping for here. If the file is an interactive PDF, you cannot edit it in InDesign. You can try the Acrobat forum to see if you can get some help there.

[James Gifford—NitroPress]

Just editorial here, but if your goal is to sell on Amazon/KDP, note that sales of such non-books are essentially zero, and that's after you get through the proof and approval steps, which are increasingly loaded against "low content books" such as this. The market was vastly over-flooded years ago.