Potential challenges: Some parts might involve copyright issues if people are sharing unlicensed copies. It's important to emphasize legal sources and respect copyright laws.

I should verify if there are any notable authors or publications known for this book. If not, keep it general. Maybe mention that it's a commonly used resource, hence the demand for an updated PDF version.

I should also check if there are any specific chapters or topics covered in the "kambi kadakal" part. Maybe it's a specific section in the grammar book focusing on sentence construction. Examples would include how different sentence structures are presented, perhaps with exercises.

Potential mistakes to avoid: Assuming all PDFs are the same. There might be different editions or authors, so advising to check sources is important. Also, not all PDF versions might have the same quality or completeness as the physical book.