If the document you bought requires Findel Font, the seller likely used a pirated or internal version. You cannot fix the missing file; you must replace it.
But what exactly is the Findel Font? Where did it come from? Why is it so hard to find for official download? And most importantly, what can you use instead?
Since you cannot legally download the official Findel Font for home use, you need the next best thing. The following fonts closely mimic the aesthetic—friendly, educational, sans-serif, and highly legible.