Best Software for Outlines with Graphics

I am seeking advice for a software solution for academics.
To organize my research data when I'm writing articles and chapters, I find it easiest to just cut and paste off relevant PDF files (both images and text), directly into MS Word. I create outlines in word, and then plug in the appropriate research data under the various headings.
Now, the difficulty with Word is that it crashes when documents get around 100 MB. So I end up having to create a ton of smaller Word documents, for every chapter/article outline I make. What I am looking for is software that offers powerful outlining capabilities, combined with very powerful graphics functions. This will enable me to make one very large chapter/article outline, and will be much better (and faster) to work with.
It has been suggested, as a solution, to make my PDF's smaller. This solution, however, does not work, because I have over 3000 PDF files that I work with on a regular basis. And I can't get them all to a small enough size to prevent Word from crashing.
Another solution is to OCR my PDF's, and just cut and paste text. However, my PDF's are often scanned graphics files, in addition to textual files from the 1800s. They do not convert well through OCR.
A third solution is to use Indesign by Adobe. However, after downloading the trial version of this software, I have realized that the learning curve on it is extremely steep - and even then, I'm not sure that the outlining function is powerful enough for my needs. I need to make outlines that are easy to manipulate, and that have at least 5-6 subheadings per major heading.
Can you direct me to any other solutions?

I don't understand why Word is crashing when the file reaches 100 MB? Nowadays, that's a small file. I routinely create Word files that size without crashing. I'm using Word 2011 with the latest service packs installed. Which version of Word are you using?

In any event, if you're looking for a powerful WP program that incorporates the features you mentioned, you might be interested in Scrivener. It's $45 but they do have a trial version for free download. Here is the LINK.

Thanks for your response. Yes, 100 MB is a bit small, so I checked my most recent file and it was about 600 MB. So I'm thinking I need a software program that can handle outlines of up to 1 GB or more, with tons of graphics and writing going on.
I looked at scrivener and it has possibilities. Mostly though I'm worried that it won't be able to handle the pasted PDf graphics in the outline without crashing. But I'll give it a try. Thanks.

I'm running Word for Mac 2011; and have a 2011 iMac with quad core processor, so I think i have the right hardware for such things...

Let us know if you give Scrivener a try. It's designed for large documents and manuscripts. Many professional writers use it because of its ability to handle large documents.

I noticed you did reply back that your Word document was 600 MB. I would think Word could handle it, but since I never work with documents that large I have no first hand experience.

I tried it last night, and it does not appear to be the type of software I need. I'm really looking for a very strong outlining function, where I can paste graphics underneath headings, where I can move headings around at will, and where I can have at least 5 or 6 subheadings. I also like to be able to expand and collapse items in the outline, so that I can see my outline at a glance, as well as with some sections expanded and collapsed, at any given time. This, to me, is the most intuitive and fastest way to keep an outline organized for writing academic chapters and articles. If you have any other solutions please let me know.

I used Papyrus for publishing a book six years ago. It has many of the capabilities you desire. It was easy to reposition with the outline, and photos (and captions) moved and updated almost instantly. How large the file can be? Not sure, but it is RAM based so much faster than MS Word or any of the others. It is available for both Windows and Mac. If I were to publish another book like that, that would be my choice. While it hasn’t been updated for a while, it does work with Lion.

I've been looking into scrivener again, and it may have the capabilities I need. So long as it doesn't crash when the project size gets over 2 GB, it should be a reasonable solution. I'll keep my fingers crossed! Thanks to everyone for their helpful and thoughtful replies - much appreciated.