How to merge 3 files?

I can think of a couple of ways to do it.

Way 1:
Create a document the same width as your pages but 3 times as high. Then drag your pages into this document so that they are page 1,2 and 3 from top to bottom. Then save as a PDF.

Way 2:
Select all three pages for printing, but instead of doing an actual print, print to a utility like CutePDF (free).

That was the first thing that came to my mind, but while writing it up I realized that the resulting document would be a single page.  Perhaps I am mistaken, but I don't think a PDF reader would present it as 3 pages.  To get the pagination information into the file I thought a merge utility would be the way to go.

I use the free version of pdfCreator to convert documents to a PDF.  pdfCreator installs a virtual printer and comes up as one of your printer options whenever you do File->Print in any application that you can print from.

So the way I would do what you need is:

1. Download and install pdfCreator

2.  Export each page to a separate .jpg sized at 300ppi for the physical paper size you will be printing to.  From your description your pages are already correctly sized.

3.  Open any word processing application you have. (MS Word, LibreOffice, whatever).  Personally I use the free open source LibreOffice.

4. Create a blank document in the word processor.

5. Import each of the 3 jpg's into a separate page of the word processor document.

6.  Save the single, 3 page word processor document for later use if required.

7.  Select File->print in the word processor. After installing pdfCreator, pdfCreator will appear as an option in your list of printers.

8. Select the pdfCreator printer from your list of printers.  Then follow the prompts to choose the output filename for the pdf and the folder to save it in.

Now you have a pdf file with each image on a separate page and sized appropriately.  You then print the pdf as any other pdf file (double sided/singled sided pages etc)

it's horses for courses.

For me, pdfCreator is much cleaner.  Out of curiosity I tried to download the free cutePDF.  During installation it forced me to make tecoma my browser's home page before it would continue. It then told me that cutePDF must run with another utility (PS2PDF or something similar) and asked my permission to download and install it automatically.  I clicked Yes but then immediately cancelled it because I would not have the opportunity to scan the "extra" utility for viruses, trojan horses etc before installing it.

Downloading files without being able to scan them before running them is a big NO-NO for me.

I will stick with pdfCreator.  I have been using it for years now and trust it and it works very well with all my applications that I can print from .

If you're more comfortable with cutePDF, that's fine with me

I am  sure readers are more than capable of choosing for themselves which converter they prefer to use to meet their risk level and requirements

If you use Windows 10 you can print, one or more pages of image files, to a single PDF using Elements.

In Elements Print window select Microsoft Print to PDF in the Select Printer section.

Tested using Elements 12 & 15.

For those not using Win 10, you can do the same thing as Moto suggests by installing a virtual printer.  My personal preference is pdfCreator (as posted earlier). It appears as a printer option when you do File->Print (I'm using PSE 14).

Just make sure you select the images first in the Photo Bin. Then set any printing parameters as required.  Each image is then saved to a separate page in a PDF file when pdfCreator is selected as the printer. This way is a little quicker than the steps I posted earlier but I prefer the extra steps that suit my workflow when producing flyers/news sheets etc.