Two PDFs side by side

There are free software options that can merge 2 PDF files. (I have a pro version that does it, so unfortunately, I don't have any information to give you about that).

Then to display 2 pages side by side in Acrobat Reader, go to the menu "View/Page Display/Two Pages"

I knew it existed!
https://pdfsam.org/ (split and merge)

For merging multiple PDFs into one, it's here http://www.ilovepdf.com/en/
Then for those who wish to display the pages side by side in pairs, in Adobe Reader you have to go to: View / Page Display / Two Pages (yes, I finally found it... I had found it but it didn't work at first, I don't know why) anyway! Here you go :)

Hi,

To merge two or more PDFs together, there is pdfblender which works very well and is free. Combined with cutepdf, you can practically do everything.

For very large PDFs, I recommend using Foxit which will be much lighter than Adobe Reader.

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I hope I was able to help you. Good luck!!!
"He who said that money does not bring happiness must have had a serious problem$$$$$"

Yes, it's possible, but the pages need to be in sequence in the PDF. So before you can do that, you have to combine all the pages into a single PDF file. I believe there are free software options that can do that.

Then in Acrobat Reader, use the option to print multiple pages per sheet (with the right settings), which will allow you to print two A4 pages on an A3 or two A5 pages on an A4.... and with the "scaling" option, you can force an A4 format to fit into an A5.

There are other paid methods... but there might also be other free ones...