The PDF to JPG tool detects, on the client before upload, a PDF that needs a password to open and shows a password-protected error instead of uploading it.
An Adobe Community discussion states that PDFs requiring a password to open cannot be converted until the password protection is removed. removing protection from a pdf file
PDF To JPGConvert Password Protected PDF To JPG
The PDF to JPG API route has no password or decryption handling; it passes the uploaded file straight into a Ghostscript command that assumes an unencrypted PDF.
Open the PDF in a desktop application to remove the password.
Save the file as a new unencrypted PDF.
Upload the new PDF file to the conversion form.
Checking The JPG Output
Download the finished JPG images from the results screen.
Open the JPG files to review the visual quality.
Continue with Select Specific Pages or Convert On iPhone.
Frequently Asked Questions about Convert Password Protected PDF To JPG
How do I fix the password-protected error?
Remove the password from the PDF using a desktop application before uploading.
Where do I upload the file after removing the password?
Upload the unencrypted PDF to the PDF To JPG form.
How do I get the JPG files?
Download the JPG images from the results screen.
What should I do if the conversion fails again?
Try the conversion again with a freshly saved, unencrypted copy.