SEC Filing Details Document Details Form PRE 14A Filing Date Mar 8, 2024 Document Date May 2, 2024 Form Description A preliminary proxy statement providing notification matters to be brought to a vote Filing Group Proxy Filings Company Koppers Holdings, Inc. Issuer Koppers Holdings Inc. Filing Formats iXBRL View HTML Download PDF Download DOC Download XLS XBRL XBRL Viewer EX-101.SCH - XBRL TAXONOMY EXTENSION SCHEMA EX-101.DEF - XBRL TAXONOMY EXTENSION DEFINITION LINKBASE EX-101.LAB - XBRL TAXONOMY EXTENSION LABEL LINKBASE EX-101.PRE - XBRL TAXONOMY EXTENSION PRESENTATION LINKBASE XML - XBRL INSTANCE DOCUMENT