SAN FRANCISCO (AP) ¿ A software company is suing Palm Inc., claiming the handset maker infringed on its copyright for a reader of PDF-format documents. San Rafael-based Artifex Software Inc. said Friday it filed a suit in the U.S. District Court for northern California because Palm had integrated its muPDF program into Palm Pre devices since their launch in June. Artifex said Palm documents indicate the company uses muPDF but said it has not obtained a commercial license from Artifex. MuPDF is freely available on the Internet but is restricted from being used in commercial products. A Palm representative did not immediately return a message left seeking comment. Palm shares closed up 22 cents, or 1.9 percent, at $11.73 on Friday.