The Norton Critical Edition of The Metamorphosis uses the Corngold translation. While not a free PDF, many libraries have a "scan-on-demand" service. You can request that a librarian scan specific pages (for fair use, e.g., 10% of the book) and send you a PDF.
Most translations famously begin with Gregor Samsa waking up as a "giant insect" or "cockroach". Corngold digs deeper into the original German term Ungeziefer the metamorphosis pdf stanley corngold