In ODOO 15, you can use the e-signature app to send several documents for signature to customers. To streamline the process and save time, you can use tags to define the type of file, the role to use, and the width and height of the signature field in the PDF.

Here are the steps you can follow to set this up:

1. Create the template for the PDF document: In this step, you will create the template for the PDF document that you want to send for signature. This template should include placeholders for the signature field, where you can insert the tags.

2. Define the tags: The tags are used to define the type of file, the role to use, and the width and height of the signature field. You can use different tags for different types of documents, or the same tag for all documents.

3. Use the tags in the template: Once you have defined the tags, you can use them in the template to specify where the signature field should be inserted in the PDF.

4. Create the PDF document: Now, you can use the template to create the PDF document that you want to send for signature. The tags will be replaced with the actual signature field.

5. Upload the PDF document: Once the PDF document is created, you can upload it to the e-signature app in Odoo. The app will automatically add the signature field in the right place, based on the tags that you defined.

6. Send the PDF document for signature: After uploading the PDF document, you can send it to the customer for signature.

Please note that you may need to install the e-signature app and configure it before you can use it. Also, the above steps are general, and you will need to check the documentation of the e-signature app you are using, as different apps may have different ways of handling the tags and the signature fields.