Automator: Download invoices (PDFs) from Websites in the backgroud

Automator is not your friend here.

Automator can be used to download a set of URLs, but it works well for preset URLs, but fails miserably when it comes to logically and dynamically determining a variable file name (e.g. file names that vary by date).

The second issue is going to be the nature of the documents - as tax documents they're not likely to be public, so they're going to be behind some authentication system, and getting Automator to push through that is going to be a challenge.

IF you can wean a set of URLs, then it may be possible to get Automator to drive Safari to initiate the downloads, but that's about the extent of what you'll be able to do.

You might get a little further with Shortcuts, but my inclination is that you need to go deeper, with something like AppleScript which has actual logic tools available for sorting out some of the nuances of what you're asking for.

The following curl syntax would silently download an explicit PDF file location on a remote web service to a local filename:

curl -s https://some/path/to/foo.pdf -o localfoo.pdf

There must be a specific PDF filename in that URL path because if the PDF is being served by a website using Content Management Software (CMS) such as Drupal, it will hide the actual PDF filename behind a link, and curl won't fetch that PDF.

More problematic is how you can check the last modified date of that remote PDF invoice before code logic determines it can be downloaded.

And, you can get the last modified date of the Invoice pdf on the remote server using this curl sequence. It does not download the file.

curl -s -v -X HEAD https://some/path/to/foo.pdf |& awk '/< Last-Modified: / {print substr($0, index($0, $3))}'

Wed, 27 Feb 2013 20:26:38 GMT

Or Zsh and either wget or cURL command line tools… to be completely headless without a browser…

For AppleScript, you might try entering :macScripter in a Google search. It should be the first search hit. This is the revived MacScripter site which has AppleScript and AppleScript/Objective-C solutions.

For Zsh, you are probably looking at Google again, though most script-related responses are for Bash shells on Linux.