If you want a really nice, small, fast app to do that: you cannot really go past PDFArranger on Github. There is no real reason to pile it's features into SumatraPDF.
SumatraPDF is a tiny and speedy PDF reader in the first place. I hope that it stays like that. Don't ask for features that - other PDF tools (performing very well and speedy) already have. - will make SumatraPDF "the Swiss knife for ALL your PDF needs" I hope that the author keeps SumatraPDF doing a couple of things very well and speedy instead of making it doing a lot of things badly and slowly. (changing SumatraPDF into bloatware) I can't downvote, but if I could I would.
Peter Dedonder can't agree more
PDF24 creator, it is a propietary freeware and it has really everything in it.
Also extract pages.
It would make the application heavier and slower. It can be done in another app though.
Customers often send 2 documents that belong together as 2 pdf's, I would need them to be printed on one sheet of paper (duplex) so I would love if I could drag and drop a page of one pdf into the other.
Use Libreoffice Draw. Yes, I`m not mistaken. You can separate PDF by atoms :)
When producing a PDF fro a long website, I very often have to cut out the last pages with advertising and additional article offers. So deleting and rearranging would be a very usefull function.
As suggest by Milivoje Savic, pdfarranger does a good job (except killing the list of content when rearranging pages) and I changed my mind in building this into sumatra. But maybe Sumatra may use pdfarranger when installed by calling it via button in the interface. If not installed, it could offer a download.
David Göhler: Any PDF tool can be called by SumatraPDF with filename and page number (using ExternalViewers method) so there are literally dozens of ways that given the right commands an external tool can modify the PDF. Which as you note is a much much greater CPU intensive task than a fast reader has to cover. And since bookmarks are not physically part of page objects then altering order breaks the embodied links.
pdfsam is an alternative, obvious is more great we can do this from sumatra, but I sure not view it in the future :P
dominiosclave: Any PDF tool can be called by SumatraPDF with filename and page number (using ExternalViewers method) so there are literally dozens of ways that given the right commands an external tool can modify the PDF. The problem in this case is you can only nominate the one page or filename you are viewing. it is possible to then let SAM ask you for another file or which pages but that is specific to whichever single app is given the filename and page number. I use a "shim" command file to do that for me.
i upload it somewhere in the internet for merging. i split with microsoft print to pdf by printing the pages i want
Pdf arranger is a great free & open source app that does just what you need. Sumatrapdf should try to stay a dedicated reader app, small and fast.
Milivoje Savic: editing also is great with Xodo
abc: xodo is online service (one of many). Pdf arranger is standalone (offline) app.
If these features of merging, spliting and editing(also including annotations) the pdf, added in SumatraPDF, it would be make it more better since it is all what is required. It can be given as plugin for those who require it, or can access any online free service for that keeping the load and size of application approximately the same.