Bug: Polygon fills may bleed outside of their boundaries when exported to EPS, PDF, AI or SVG formats
When maps containing polygons that are very small or located at the very edge of the dataframe are exported, the polygon fills may bleed outside of the polygon boundaries. This problem occurs in exports to EPS, PDF, Adobe Illustrator, or SVG formats with polygon symbology set to line, picture, or character marker fills.
This is a known issue.
Note: This issue is addressed in ArcGIS 9.1 Service Pack 1 (SP1).