There are three options to position and align sender or signer fields while preparing a PDF on the editing page.
Fields can be dragged and dropped onto the PDF, this is the fastest but least accurate way to place fields.
Hover over a field and use the arrow keys on your keyboard to move fields already placed on PDF pixel by pixel.
Hover over a field and press Shift + (any arrow key) to snap align the field to the next closest field in the direction of the arrow key selected.
Snap align will save you a lot of time if you have a list of form fields straight down the page, or directly across the page.
Check out this article with all the tricks on form fields.