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Way to install Sumatra plugin for 32-bit Firefox on Windows


I'll discribe one posible way to install SumatraPDF browser plugin for 32-bit Firefox on Windows, so that others who had unsuccessfully tried to do so can try one more option.

1. Downlaod version 2.5.2 and install it with plugin, then download and install latest version in same folder and keep the plugin.

2. Right click on Computer icon and choose Properties, and then choose Advanced system settings from left meny.

3. Open Enviroment Variables and create New User variable for PC with folowing properties:
Variable name: MOZ_PLUGIN_PATH
Variable value: <adress of folder where is plugin>
e.g. C:\Program Files (x86)\SumatraPDF\
or C:\Program Files\SumatraPDF\

4. Open Firefox and go to Tools, Add-ons, Plugins. Set SumatraPDF Browser Plugin to Always Activate, and all others plugins for viewing pdf fomat to Never Activate.

5. Now go to Tools, Options, Applications, find Portable Document Format (PDF) and choose Use SumatraPDF Browser Plugin (in Firefox).

6. If Use SumatraPDF Browser Plugin (in Firefox) is not offered close Firefox and go to C:\Users\<username>\AppData\Roaming\Mozilla\Firefox\Profiles\<profile code> and delete mimeTypes.rdf, then open Firefox and do the step 5.

I hope that someone will find this helpful.
andrija.s.995 on February 25, 2017
This procedure is obsolete since Mozilla Firefox 52.
Beginning with version 52 Mozilla's NPAPI plugin system is disabled (with the sole exception of Adobe's Flash plugin).

So unfortunately, there is no way now to embed the Sumatra PDF Reader into Firefox. What we need is a new development for (at least) the 32 bit version of recent Firefox versions.

Even though there seem to be workarounds to continue using NPAPI plugins past Firefox 52, this is just a makeshift that may expire soon.
Tinkerer on March 9, 2017
Just to note, Waterfox still supports NPAPI plugins for as long as possible.
Waterfox is, unfortunately, 64 bit.

However, it *is* possible to get it to work. Currently, what I did is:
1. Download the source for 2.5.1.
2. Open in VS2013. (Free from Microsoft)
3. Select platform X64, "release" from the dropdowns.
4. Compile it(nothing else seems to be needed)
5. Find the compiled "obj-rel64/npPdfViewer.dll" and rename it to "npPdfViewer64.dll"
6. Copy this file to your 32-bit or 64-bit Sumatra installation(I'm using 3.0 which I could only get in 32-bit)
7. Run this command: %WINDIR%\syswow64\regsvr32 "C:\Program Files (x86)\SumatraPDF\npPdfViewer64.dll" (change the sumatra path if needed)
8. Provided everything worked, SumatraPDF will now show up as a plugin in Waterfox.
I was surprised that the 64-bit plugin DLL would load the 32-bit Sumatra exe, but it seems to work just fine(tested on Win 7 and Win 10)

It's a shame it's so hard(I wish someone would compile and host that 64 bit dll), but it *does* work.
Hopefully this will get us through a couple more years before some better solution comes out - Firefox's built in PDF viewer is *not* the solution!
Macrobb on March 30, 2017

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