Merge several PNG files into 1 file

I have 900 separate PNG files that I would like to merge into 1 file.

In other words, I want to be able to open the file and have 900 "pages"

I know how to do this with a PDF but it doesn't seem to work with PNG files in Preview.

PNG isn't really format that supports the concept of pages. You'd effectively end up with a single image.

if you're looking to do a collage.. maybe try something like this http://www.shapecollage.com/

I don't want a collage.

I want to be able to scroll down and see the images.

Basically, I am doing research on Facebook content and I have done screen shots of several months of posts (not my own). I want to take these images and just put them into 1 file...á la 900 pages in 1 file. This would allow me to scroll through the pages and read the content.

This was the only way I could save the content from last year posted on FB.

So, I don't want to do anything with the images other than put then all in one file rather than having 900 files in a folder.

One option may be to convert the PNG files to PDF and then just combine them into 1 file since that is feasible.

However, now I have to find a free batch converter from PNG to PDF.

I checked out Automator but the Change type of Image option does not have PDF as an option.

I solved my problem.

I had 1527 screen shots in PNG format
Downloaded Dragoman (Download Dragoman for Mac - Batch file converter for images, photos, music, sound, archive files. MacUpdate.com) and converted all into PDF format, which took less than 5 minutes
Opened and combined all the PDF files in Preview, which took about 20 minutes

Probably not the nicest and cleanest way of doing what I wanted, but it worked.

@Trolle, I managed to create a workflow application to convert many of the screenshot png files into a single pdf. 1) Ask for finder items, and check the "allow multiple selections" box. 2) New PDF from Images- and to rename the pdf each time make sure to select "show this action when the workflow runs." Then save as application.