Question: I took a bunch of screenshots and I want to make them pages in a single PDF. Selecting all four in Preview and exporting to PDF only exports two (?), separately. The "Export to PDF" File menu function adds a strange white border around the screenshots (and orients the page as portrait). So I converted each to PDFs individually and then combined them manually. I tried the solutions [here](https://apple.stackexchange.com/q/11163/21351), but Mavericks' Preview doesn't appear to work that way anymore. What's the best, free, hopefully built-in way to automate this?

Answer: 
There is an Automator action - **New PDF from images**. It creates a single multi-page document from input images. You can create a workflow or app that would process your images that you drop onto it.

If I create an application in Automator with that single action, I can drop my images onto it, and it'll create a PDF with one page per image.
Preview's "Export As PDF..." places the converted image onto the default paper size, e.g. A4 or US Letter. That's why you get the "strange white border" around the image.

Using Preview's "Export..." menu item, and selecting PDF as the format will merely convert the image to PDF without placing it on a page.

Apple's Automator action "New PDF from Images" works well, but suffers from Automator's limitations in where output files can be saved.

A python script that will combine images (supplied as arguments) into a PDF file [can be found here](https://github.com/benwiggy/PDFsuite/blob/master/Automator_Scripts/image2pdf.py). It can be used in an Automator "Run Shell Script" action to create a Quick Action/Service.