Update PDF support details in documentation

Added information about PDF decoding limitations and licensing.

Author: yqz562

barcode-reader/general/dbr-supports-pdf.md

@@ -8,6 +8,14 @@ needAutoGenerateSidebar: false
 
 ## Can Barcode Reader SDK read PDF files? Do I need to pay for this feature?
 
-Dynamsoft Barcode Reader does indeed support reading barcodes from PDF files (see [Features](https://www.dynamsoft.com/barcode-reader/features/#Decode-Barcodes)). The only exception is the JavaScript and Mobile editions currently.
+Yes — **Dynamsoft Barcode Reader supports reading barcodes from PDF files** in most editions (see the official [Features](https://www.dynamsoft.com/barcode-reader/features/#Decode-Barcodes) page).  
+The **only exceptions** are the **JavaScript edition** and the **Mobile edition**, which currently do **not** support PDF decoding.
 
-No extra license is required to read from PDF files.
+### Do I need an extra license to read PDF files?
+No. **Reading from PDF files does not require any additional license**. It is fully included in the standard SDK license.
+
+### Additional Note: Multithreading Limitation
+Please be aware that **PDF decoding does not support multithreading**.  
+Even if your application uses multiple threads, PDF files will still be processed **single-threaded** due to the way PDF pages are handled internally.
+
+If you need higher performance, it is recommended to **convert PDF pages into images** and then decode them in parallel.