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What is the most straightforward way of modifying PDF start-up options via C#?

I'd like to know what would be the most straightforward (i.e., preferably without adding DLLs to my solution) way to write a C# code snippet for modifying a PDF document's page layout and magnification options.
I know this is incredibly easy in LaTeX (well, it's easy to set these for a PDF to-be-generated using a single package) through hyperref options.
Modifying an already-created PDF document is a lot more work however. Also, most MS Office print-to-PDF options don't seem to include this ability while it's obviously annoying to keep opening documents up in Acrobat and manually modifying these for the proper (desired) opening settings (layout: single page, and magnification: fit page, for me).
So, I would like to write a code snippet that could do this. What is the most straightforward way of modifying PDF start-up options via C#?
Alternatively, is there a way to force-apply these options when generating PDFs from MS Office software suites?
I looked into PDFSharp and MigraDoc at one point for PDF-making from C#, but that really didn't match what I was hoping for. Plus, it added a DLL set (of ten dependencies) which was sub-optimal with respect to how many ancillary files were included with the build for managing a relatively simple function.
However, as noted in the comments, such a batch modification code is likely to be very difficult without any dependencies, so I'll also accept answers which reference dependencies.
Past topics (but not very good matches):
This is similar but for JavaScript, and actually suggests it shouldn't be done.
This is a bit more elaborate for JavaScript, but not exactly what I am looking for.
This topic seems to be this question for PHP but including some external references...

Edit HTML files manipulating DOM in a jQuery style

I have a batch of HTML files which need some editions easy to perform with jQuery (mainly selecting some nodes and changing their attributes).
My approach to achive this, has been opening them one by one in Google Chrome, excecuting the jQuery code in the console, and then copying the resulting DOM back to my HTML editor.
Since what I'm currently doing takes a lot of time, and also due to the fact that every file needs the same edition (i.e., the same jQuery/JS code will work for every HTML file), I am considering to write a script/program to do this.
Anyway, I am not completely clear of which of the following (if any of them) approaches I should take to accomplish this task.
Write a JavaScript script with jQuery using some FileSystem/File manipulation library (which one?)
Write a Java or C# program using some jQuery-based library (like CsQuery)
Finding a plugin for some of my editors (Aptana, Notepad++, Eclipse, etc) or a completely different editor that supports jQuery-like commands for edition (just as notepad++ regex replacement support). This would be slow with big batches, but at least it would allow me to avoid the annoying copy/paste to/from Chrome.
Is one of this approaches the right way to accomplish what I need? (Is there a right way to do this?) Which should be more straight-forward?
I think that #2 would be easier for me since I have a lot more experience in Java and C# than in JavaScript, but I think that maybe that idea would be sort of using a sledgehammer to crack a nut.

You should consider using PhantomJs. It is a headless WebKit which can be executed from te commandline. It accepts a javascript or coffeescript file as a an argument, which can be used to e.g. do something with a web page. Here is an example:
var page = require('webpage').create();
page.open('http://m.bing.com', function(status) {
var title = page.evaluate(function(s) {
return document.querySelector(s).innerText;
}, 'title');
console.log(title);
phantom.exit();
});

I am not sure of the right way but it sounds like you are familiar with C# and would think writing a class library would be the least overhead for automation. Here are some potential solutions:
Scripting Library (e.g., C#.NET) - You can use a library like the one you mentioned or something like ScriptSharp if you want to use DOM manipulation. If the HTML has appropriate closing tags you can also use LINQ to easily navigate the HTML (or something like the HTML Agility Pack found on CodePlex). I would even recommend using Mustache with an HTML file template in C#.
JavaScript Library - If you wanted to stay in pure JavaScript you can use Node.js. There are file manipulation libraries you can use.
Headless Browsers - Haven't thought through being able to save the resulting HTML automatically but you can use something like jsTestDriver or Phantom.js
You can go with the plugins in editors as well, but I would stick with a Java, C#, python, etc. library that you can potentially call from existing application or schedule as a job/service.

How to get installed image editors

Is there a code to get all the image editing software the user has installed?
I would like to know how to list all the applications by going through registry, is there any way to then filter out only the apps that can edit images, like Paint, Photoshop, etc...?
Thanks!

Here is an example for any generic file type:
How to get recommended programs associated with file extension in C#
If you look for jpg, png, etc. you'll get image editors.

No.
There is no expectation that every application developer somehow places metadata tags for their application inside of the registry (or wherever)... and, if for some reaosn a few handful of application developers did there is no way to guarantee the consistancy. Not to mention that application developers don't always use the common words you'd expect for their applications... Not every image editing application has the word "Photo" in it (for example, Picasa from Google).
The best you can hope for is to build some keywords to look for, add in a list of famous applications that don't conform to the keyword conventions your expecting ("Paint", "Photo", "Image", etc.), and work with that... either that or create a large database yourself to check against. Also, as other answers/comments have indicated, looking for applications that are used for specific extensions is helpful.
Nothing guaranteed though.

Multiple Image Uploading / Map Images to Products

I am looking for a solution (APIs, etc.) for handling a similar experience as cafepress.com. I need to be able to upload images (preferably multiple at a time) and be able to map my uploaded images to various product images (clean stock images of shirts, mugs, etc.). I also want to give the user some very basic controls over the images they upload such as cropping, resizing, levels, etc. Any suggested libraries or APIs would be greatly appreciated. I am looking for .NET solutions (if server-side). I am not looking for how to tie this all together but rather some suggested libraries or tools to build out some of this functionality.
Note: If this is not the place for this type of question, please move accordingly or suggest an alternate site.

Frankly, I don't think you are going to find what you are looking for specifically, unless you are looking at using a full on CMS of some form. Frankly, those problem domains are too far apart. Instead you should probably look at them as individual pieces.
So far as upload controls exist, there are probably close to 100, some free some not so free. Personally, I already have a Telerik subscription, so it was a no-brainer for me, but Rad Upload works well and supports multiple uploads. Free implementations are available.
The cropping and post image handling tasks ( at least the ones you have listed ), can easily be handled using standard System.Drawing.* calls, or if it gets more advanced a ton of free libraries exist, like the age old ImageMagick, but there are a number of commerical libraries available as well. Chances are though, the inbuilt libraries will be more than sufficient.
Finally the mapping to products should be handled by your business layer ( aka, code you write ) as it is going to be so specific to your app.
However, if you are looking for a storefront or CMM with a multiple image upload control, that is a very different question with many options as well, both free and commercial.

use openCV. you can find it here: http://opencv.willowgarage.com/wiki/
you can use this library perfectly with c++.
if you need to use it in C# use this wrapper: www.emgu.com/wiki/index.php/Main_Page

.NET open PDF in winform without external dependencies

Is there a FREE library which will allow me to open a pdf and show it on a winform project. I know I could open it in adobe reader or something but it always seems so bloated to me and I would be relying on it being installed. Is there a nice lightweight alternative where I could just include a dll in my project or similar avoiding external dependencies.
I don't need much functionality just view, change page zoom..
I have seen a few libraries but they seem to be about creating PDF's not viewing.

I'm not sure what you call a 'dependency' since you'll always have to rely on some external code to render the PDF unless you bundle the whole PDF rendering source inside your project.
There are some commercial renderers and very few free ones.
If you want to avoid dependencies that you can't bundle then maybe you could have a look at the source code for SumatraPDF, an OpenSource PDF viewer for windows that uses MuPDF.
There is also Poppler, a rendering engine that uses Xpdf as a rendering engine.
All of these are great but they will require a fair amount of commitment to make make them work and interface with .Net.
Most other open source libraries are only used for creating and managing PDF pages and I don't know any that actually does rendering; it's such a hard problem to solve right.
You may still want to consider using GhostScript as an interpreter because rendering pages is a fairly simple process.
The drawback is that you will need to either re-package it to install it with your app, or make it a pre-requisite (or at least a part of your install process).
It's not a big challenge, and it's certainly easier than having to massage the other rendering engines into .Net.
Have a look at this SO question I answered today.
It contains some more information and a link to some working .Net code I posted on another forum a few months ago.

First you need to reference the Adobe Reader ActiveX Control
Adobe Acrobat Browser Control Type Library 1.0
%programfiles&\Common Files\Adobe\Acrobat\ActiveX\AcroPDF.dll
Then you just drag it into your Windows Form from the Toolbox.
And use some code like this to initialize the ActiveX Control.
private void InitializeAdobe(string filePath)
{
try
{
this.axAcroPDF1.LoadFile(filePath);
this.axAcroPDF1.src = filePath;
this.axAcroPDF1.setShowToolbar(false);
this.axAcroPDF1.setView("FitH");
this.axAcroPDF1.setLayoutMode("SinglePage");
this.axAcroPDF1.Show();
}
catch (Exception ex)
{
throw;
}
}
Make sure when your Form closes that you dispose of the ActiveX Control
this.axAcroPDF1.Dispose();
this.axAcroPDF1 = null;
otherwise Acrobat might be left lying around.

I would look into Foxit Reader as a lightweight alternative to Adobe Reader. It consists of a single .exe file that you can bundle with your application and thus shouldn't require any installation. According to their EULA this is allowed, as long as your application is not installed on mobile devices. All you would have to do is launch the reader as a new process, pointing to the appropriate pdf. Obviously the downside to this approach is it won't be integrated into your application's interface.

The ActiveX control installed with acrobat reader should work, either drop it in via the designer or use something like this.
This will require the relevant version of the reader is installed on the client but since you indicate that you could just launch that anyway this should not be a problem. reader

Take a look at this. It requires quite a few libraries (including GhostScript), so it's not terribly light weight. But all dependencies included native reading of PDF. It's in VB--but could be translated if you need C#:
http://www.codeproject.com/Articles/37458/PDF-Viewer-Control-Without-Acrobat-Reader-Installe

There is a free PDF library. It is mainly editing the contents but it might help.

This is a guess.
The way browser render PDF inside it with a plug-in. I am not sure whether it requires the application to be installed.
You can use Foxit reader OR Sumatra PDF.
And, you can host the browser control on your winform.

Put a webBrowser control on your form.
strPdfFile = "C:\SomeFile.pdf"
webBrowser.Url = new Uri(strPdfFile);
This is worked for us until tried on a Win7-64bit system. Need to do some debugging now.

You can use Spire.PDFViewer from Nuget. See here