How to merge multiple image files into one pdf file with page and its original size for every image

Adobe Reader can do this, too: It includes a Poster Print option in its custom print dialog.

It’s the first time I missed a feature from Preview (or the native OS X print dialog) that Adobe Reader has.

Adobe Reader is free (as in beer) software, it used to be called Acrobat Reader. (Do not confuse it with full-blown Acrobat or any other expensive Adobe product, which can probably do that, too.)

Here is how to use Safari to print an image to span multiple pages:

1) Open the image to be printed in Safari. If it is a local file, then choose File -> Open File.... Or if you already have the file open in Preview, you can drag the icon of the file from the title bar of the Preview window onto the Safari window or Safari icon in the dock. Otherwise, load the image from the Internet however you usually would.

2) Go to File -> Print... and then change the Scale (%) so that the image is the desired size. If you do not see the place to change the Scale, you may need to press the Show Details button. Safari will show you a preview of how the image will appear on each page, so you can see how big the resulting image will be. For the example, you can get the entire width on a single page, but the image will span 2 pages in length.

You may want to choose borderless printing if your printer supports it. For instance, for my Canon inkjet, I set the paper size to US Letter (borderless). However, I was not successful in achieving borderless printing in my one trial; Safari still left white borders around the image that I later had to trim.

3) Click print. Collect your prize from the printer. Trim away white space and then combine the different pages using tape, etc.