You downloaded a 'sample' PDF and every alternate page carries a 'SAMPLE — NOT FOR DISTRIBUTION' watermark. Either you need to remove those pages or remove the watermark.
Delete removes the entire page. To strip just the watermark while keeping content, use redact or edit PDF instead. Pick the right tool for your case.
When deleting the page is right
If watermarked pages are sample-only content with nothing of value (placeholder pages, blank watermarked sheets), delete is fine. Open delete PDF pages, select the watermarked pages by sight, delete, save.
When you need to keep content but remove the watermark
If the watermarked pages have content you need (and you have rights to use them), removing the watermark requires editing, not deletion. Use redact PDF to permanently cover the watermark, or edit PDF to remove watermark layers if the PDF stores them separately.
Identifying watermarked pages
Watermarks are usually visible in thumbnail previews. Scroll the grid in delete PDF pages and click any page showing the watermark. If watermarks are subtle (light grey, small text), you may need to zoom in — click a thumbnail for a larger preview.
Legality reminder
Watermarks usually signal restricted content. 'SAMPLE — NOT FOR DISTRIBUTION' means exactly that. Removing or deleting watermarked pages from material you don't have rights to use is risky. Check the licence.
FAQ
Can Flint auto-detect watermarked pages?
Not currently. You identify visually and select.
What if the watermark is on every page?
Then deleting all watermarked pages = deleting all pages. Use redact or get a clean source.
Are PDF watermarks easy to remove?
Depends. Some are simple overlays removable by editing. Others are baked into the page rendering. Try edit PDF first.
Difference between watermark and stamp?
Watermarks are background, stamps are foreground. Both can be removed by editing if they're separate layers; both require redaction if they're baked in.
Right tool, right job. Delete watermarked pages — or redact if you need to keep the content.