Supposing you want to convert all docx documents from a folder as shown in the below screenshot to doc documents, you can quickly get it done as follows:

1. Launch the Microsoft Word application, and then apply this utility by clicking Kutools Plus > Doc/Docx.

2. In the Document Format Converter dialog box, please configure the settings as below screenshot shown.

(1): Select Convert Docx to Doc from the Format Convert drop-down list.

(2): Click  > Files or Folder to select documents you will convert to .doc documents.

(3): Click the Browse button  to specify the output directory that you will save the new documents into.

(4): It's optional to tick the Delete source files after conversion option.

(5): It's optional to tick the Keep the modified date of original files option.

3. Click the Ok button to begin converting.

Then you will see all results as below screenshots shown.

If you have a folder with many doc documents as shown in the below screenshot, and you want to convert them to docx documents at once, you can get it done as follow:

1. Please launch Microsoft Word application and then click Kutools Plus > Doc/Docx, it will display a Document Format Converter dialog.

2. In the Document Format Converter dialog, please configure the settings as below screenshot shown.

(1): Select Convert Doc to Docx from the Format Convert drop-down list.

(2): Click  > Files or Folder to select documents you will convert to .docx documents.

(3): Click the Browse button  to specify the output directory that you will save the new documents into.

(4): It's optional to tick the Delete source files after conversion option.

(5): It's optional to tick the Keep the modified date of original files option.

3. Click the Ok button.

Then all doc documents in the selected folder are converted to docx documents in bulk at once. See screenshot:

If you want to convert all docx documents from a folder as shown in the below screenshot to pdf documents, please do as follows:

1. Launch the Microsoft Word application, and then apply this utility by clicking Kutools Plus > Doc/Docx.

2. In the Document Format Converter dialog box, please configure the settings as follows:

(1): Select Convert Docx to PDF from the Format Convert drop-down list.

(2): Click  > Files or Folder to select documents you will convert to .pdf documents.

(3): Click the Browse button  to specify the output directory that you will save the new documents into.

(4): It's optional to tick the Delete source files after conversion option.

(5): It's optional to tick the Keep the modified date of original files option.

3. Click the Ok button to begin converting.

Then you will see all results as show in the below screenshots.