If "Jack" refers to a specific topic, person, or character you're writing about, here are some considerations:
Here’s a simple protocol that has saved my sanity (and GPA): jack or the submission pdf
Q: Does "jack" refer to a person named Jack? A: Almost certainly not. While urban legends mention a Dr. Jack Reilly who first coded submission systems, the term is an acronym or a shortened noun, not a proper name. If "Jack" refers to a specific topic, person,
Q: Can I ignore the warning and submit anyway? A: You can, but the system will likely generate a low-quality proof, or the editor will return it without review. The warning exists because downstream production systems will fail. Jack Reilly who first coded submission systems, the
Q: What if my PDF has no forms but the error persists? A: Check for digital signatures. A signed PDF is locked, but the jacket might still be editable. Remove the signature, flatten, then re-sign after submission (if required).
Q: Does this apply to LaTeX-generated PDFs?
A: Less often, because LaTeX outputs are typically flat. However, if you use \pdfinfo commands, you are creating a jacket. In that case, simply omit those commands from your preamble.
Does the error occur immediately upon upload? That’s a jacket problem (metadata). Does it occur after the system "processes" the file for 10-20 seconds? That’s a content problem (tracked changes, fonts, images).