Line Art

Using the Line Art property, you can perform the following checks:

Line weight: Checks the PDF document for lines that have a stroke weight which is less than the number specified here and which occurs on more than the number of color separations specified here.
Invisible Line Art: Checks the PDF document for invisible line art images.
Nodes: Checks the PDF document for line art images or clipping paths that contain more than a specific number of nodes (anchor points).
Flatness: Checks the flatness settings of the PDF document.

Note: When processing and printing a vector image, curves present in the image are converted to a series of short straight line segments. The length of these lines are very short and your eye can only see a curve. The setting that determines the length of these straight line segments is called "flatness".
Flatness settings can be set in Adobe Photoshop, Adobe Illustrator, or other illustration programs are generally applied to clipping paths in images and on vector objects.