While the contents of your document may vary between sends, the majority of your text or signature fields may remain in the same place. Instead of re-creating all of the placeholder fields each time, you can just save a template over any document with the placeholders saved. Then, each time you go to send, just select the template, select "replace" and choose your new document to lay under the template fields.
When you upload a template to SignRequest, you can click "settings" then "replace" to change out the base document within the template. The placeholders or fields will remain in the exact same position on the new document.
You can use this feature to "prefill" documents each time with case-specific content externally, then just select the template, click "replace", and you've got a prefilled template.