Fix wrong description in PdfDocumentReaderConfig javadoc (#62)

document-readers/pdf-reader/src/main/java/org/springframework/ai/reader/pdf/config/PdfDocumentReaderConfig.java

@@ -78,7 +78,7 @@ public class PdfDocumentReaderConfig {
 
 		/**
 		 * How many pages to put in a single Document instance. 0 stands for all pages.
-		 * Defaults to 0.
+		 * Defaults to 1.
 		 * @param pagesPerDocument Number of page's content to group in single Document.
 		 * @return this builder
 		 */
@@ -130,4 +130,4 @@ public class PdfDocumentReaderConfig {
 
 	}
 
-}
+}