Firstly, download the trial version of Document Maker and install it to your SharePoint server.

And then install Document Maker add-on in Word application.

Navigate to the Absence Request List.

Under LIST tab, click Manage Templates in Settings group.

Or, in the List Settings page, click Document Maker Settings under General section.

In the Document Maker Settings page, upload absence request template in the Document Maker settings page as following.

In the Document Maker Settings page and click Rules on the left panel.

And then click Add rule.

In the Add rule page, specify a name this rule, such as absence request.

In Select Template section, select absence request template, which means that the document will be generated using this selected template.

In Naming Rule section, specify the name as following.

In Date Format section, select (Default SharePoint Format). The date format for the generated document will be same as the SharePoint format.

In Output Types section, select DOCX. The document will be generated as Word document.

In Distribute Document section, select Save as attachment option and select Overview existing documents as following.

The generated document will be saved as attachment to the corresponding item; and if the generated document already exists, the new generated document will replace the existing one when the Overwrite existing document option selected,

In Merged Document Generation section, unselect Enable option.

Click OK to save the settings for this rule.

And then, you will find that a rule is created in the Document Maker Settings page.

Navigate to Absence Request List, select one item (Cynthia Carey), under ITEMS tab and click Generate Document in Document Maker group.

When Generate Document dialog appears, in Template section, select absence request template. In File Name section, you will see that the file name is generated based on the rule as following.

Click Generate button. Wait for a few seconds, and then the document is generated as Word document, and Attachment indicates that the generated document is saved as item attachment.

View the item Cynthia Carey, you will find that the generated document is saved as attachment as following.

Modify the To field to 1/30/2018 of item Cynthia Carey and click Generate Document command to re-generate document.

And then you will find that the new generated document has replaced the existing one in item attachment.

Click the attachment and check the absence request form. The value has been updated as 1/30/2018 as following.