Looks like it might be a GPU/CPU preview problem. When you open the PDF, is the line still there?
Yes, it's a problem when i open my drawing in PDF.
Copy link to clipboard
Can you select the purple color object and choose Select > Same > Fill Color.
Then choose Pathfinder panel > Unite.
Good to hear that helped.
This can happen if you have two objects butting up against each other (for instance, the inside shape of purple and an outer shape of purple) and then Exporting as PNG or JPG with Type Optimized anti-aliasing selected. If you select Art Optimized anti-aliasing, it shouldn't happen.