Unlike classic literature (e.g., Sherlock Holmes), Kirtu comics are in the public domain. Amar Chitra Katha Private Limited still holds the copyright. Therefore, a "free" full PDF of all Kirtu comics does not exist legally. Anyone claiming to have the complete collection for free is almost certainly distributing pirated content.
The quality of the PDFs also varies, with some sources providing low-resolution scans, while others offer high-quality digital versions. Free Kirtu Comics All Pdf