typo fix: "occurence" -> "occurrence"
diff --git a/utils/pdfunite.1 b/utils/pdfunite.1
index 9b1f2e8..65bf11a 100644
--- a/utils/pdfunite.1
+++ b/utils/pdfunite.1
@@ -8,7 +8,7 @@
.I PDF-sourcefile1..PDF-sourcefilen PDF-destfile
.SH DESCRIPTION
.B pdfunite
-merges several PDF (Portable Document Format) files in order of their occurence on command line to one PDF result file.
+merges several PDF (Portable Document Format) files in order of their occurrence on command line to one PDF result file.
.TP
Neither of the PDF-sourcefile1 to PDF-sourcefilen should be encrypted.
.SH OPTIONS
