Adding PublishingPage to a specific sub-folder (in Page library)

I receive the following error
when I tried to create a new item to put within a subfolder in Page library:
"To add an item to a document library, use SPFileCollection.Add()"

therefore, I'm going to use SPFile.Add()

.........
PublishingWeb publishingWeb = PublishingWeb.GetPublishingWeb(web); PublishingPageCollection publishingPages = publishingWeb.GetPublishingPages();
PublishingPage page = publishingPages.Add(PageName, layout);
SPListItem item = page.ListItem;
item["標題"] = DTO.Topic;
item["頁面內容"] =DTO.content;
item["彙總圖像"] = imageField;
item["排程開始日期"] = PublishDate;
item["排程結束日期"] = PublishEndDate;
.....
item.Update();
SPFile spFile = page.ListItem.File;
string fileName = spFile.Name;
byte[] binFile = spFile.OpenBinary();
subFolder.Files.Add(fileName, binFile, true);
subFolder.Files[rootFolder.SubFolders[targetFolder].ServerRelativeUrl + "/" + fileName].CheckIn("checked in this Page");
subFolder.Files[rootFolder.SubFolders[targetFolder].ServerRelativeUrl + "/" + fileName].Approve("Approve this Page");