Update pdf-processing.md

Author: tony-xlh

_articles/extended-usage/pdf-processing.md

@@ -9,7 +9,7 @@ description: Dynamic Web TWAIN SDK Documentation Handle PDF Page
 
 # Processing PDFs
 
-PDFs are widely used in many and various industries, and presently are the only non-image file type that `Dynamic Web TWAIN` supports. In this next section, we will address all the input and output operations that allow the user to properly handle PDF files.
+In this next section, we will address all the input and output operations that allow the user to properly handle PDF files.
 
 ## Environment
 
@@ -29,11 +29,11 @@ To include the PDF addon, simply add a reference to the corresponding JavaScript
 
 ### Open an image-only PDF file
 
-When loading in a PDF file, `Dynamic Web TWAIN` tries to extract images from that file, which is why the SDK can handle image-based PDF documents by default. 
+If the PDF file only has one image per page, it can load the file by extracting the images. Most of the PDF files are scanned documents.
 
-### Open a searchable PDF file
+### Open a PDF file with more than images
 
-However, most existing PDF files contain much more than just images. For image-and-text PDF files, we need to make use of the PDF Rasterizer (`PDFR` for short), the main component of the PDF addon.
+If the PDF file is not pure image, we need to make use of the PDF Rasterizer (`PDFR` for short) to render the PDF first.
 
 > How PDFR works: As the name suggests, `PDFR` rasterizes a PDF file page by page much like a scanner. You set a resolution, and you get the resulting images in that resolution after the rasterization. 
 
@@ -57,11 +57,11 @@ DWTObject.Addon.PDF.SetReaderOptions({
 DWTObject.LoadImageEx("", Dynamsoft.DWT.EnumDWT_ImageType.IT_ALL, onSuccess, onFailure);
 ```
 
-The method [ `SetReaderOptions()` ](/_articles/info/api/Addon_PDF.md#setreaderoptions) configures how a PDF will be rasterized when being loaded into Dynamic Web TWAIN.
+The method [`SetReaderOptions()`](/_articles/info/api/Addon_PDF.md#setreaderoptions) configures how a PDF will be rasterized when being loaded into Dynamic Web TWAIN.
 
 #### Other methods
 
-* [ `GetReaderOptions()` ](/_articles/info/api/Addon_PDF.md#getreaderoptions): This method returns the current [`ReaderOptions`](/_articles/info/api/interfaces.md#readeroptions).
+* [`GetReaderOptions()`](/_articles/info/api/Addon_PDF.md#getreaderoptions): This method returns the current [`ReaderOptions`](/_articles/info/api/interfaces.md#readeroptions).
 
 ## Output as PDF