To determine where a downloaded PDF came from, check your browser's download history or the file's metadata. If the PDF has been saved to a computer, it will likely be in the "Downloads" folder.

Here's how to find the source:

1. Check Download History:

Review your web browser's download history to see if it lists the website from which the PDF was downloaded.

2. Examine Metadata:

Some PDFs may have metadata that includes the original source URL or author information.

3. Search the File:

If the PDF is saved on a computer, you can search the file name, content, or any embedded metadata for clues about its origin.

4. Look for a Link:

If you have the PDF open, check for a link or URL within the document itself that might point to the original source.