9. An image-reading method comprising: reading an original document as image data; displaying the image data read by the reading step; wherein a processor performs the following steps: setting a recognition target region as a part of the displayed image data; analyzing the image data and recognizing a page number in the analyzed image data of the recognition target region; determining a number of pages actually read by the reading unit; registering, the recognized page number and the number of pages in a page number table; determining a particular value by implementing a calculation in accordance with a formula (maximum page number−minimum page number +1), the maximum page number being the greatest page number among the recognized page numbers registered in the page number table, the minimum page number being the least page number among the recognized page numbers registered in the page number table; determining that a page reading error has occurred when the particular value is different from the number of pages registered in the page number table; when no page number is recognized in image data, setting a provisional page number corresponding to the image data in which no page number is recognized, and registering the provisional page number in the page number table; and when a new page number is recognized in new image data that is obtained by reading a new original document and when the new page number is equivalent to the provisional page number, changing the provisional page number in the page number table to a number different from both the page number and the new page number in the page number table.
9. An image-reading method comprising: reading an original document as image data; displaying the image data read by the reading step; wherein a processor performs the following steps: setting a recognition target region as a part of the displayed image data; analyzing the image data and recognizing a page number in the analyzed image data of the recognition target region; determining a number of pages actually read by the reading unit; registering, the recognized page number and the number of pages in a page number table; determining a particular value by implementing a calculation in accordance with a formula (maximum page number−minimum page number +1), the maximum page number being the greatest page number among the recognized page numbers registered in the page number table, the minimum page number being the least page number among the recognized page numbers registered in the page number table; determining that a page reading error has occurred when the particular value is different from the number of pages registered in the page number table; when no page number is recognized in image data, setting a provisional page number corresponding to the image data in which no page number is recognized, and registering the provisional page number in the page number table; and when a new page number is recognized in new image data that is obtained by reading a new original document and when the new page number is equivalent to the provisional page number, changing the provisional page number in the page number table to a number different from both the page number and the new page number in the page number table. 10. The image-reading method as claimed in claim 9 , further comprising handling a reading error by performing prescribed action when it is determined that the page reading error has occurred in the reading error determining step.