Common reasons PDF text cannot be copied include image PDFs, font encoding issues, viewing restrictions, and missing text information.
In an image PDF, the entire page is stored as an image, so visible letters do not exist as copyable text inside the file.
Some PDFs use unusual fonts or character encodings, which can cause garbled output or broken reading order during extraction.
Some PDFs also restrict copying or extraction through security settings.
Because this tool does not support image-only PDFs, it cannot extract text from those files.