I am writing my dissertation proposal.
I have organized all of my research under “research” and used the meta-data “category” and “status” to organize my files.
I want to compile an outline. It seems that an out line cannot be complied from the PDF title (which also happend to be the APA citation for each of my files). Is that so?

Only text documents can be compiled with the actual Compile tool, but you could use either File > Print Current Document (while the Research folder is selected and viewed in outliner) or File > Export > Outliner Contents as CSV… to create a file with the information you want. The CSV list is just a plain-text file, so you don’t need to work with it as a spreadsheet if you’d rather note; you could just open it in a word processor or text editor and wrangle it there. Print gives you the option to print to PDF as well–as I’m not sure what you want to do with the outline, that may or may not be useful. (To further customise the print version, first select File > Page Setup, then choose Scrivener from the Settings menu, and click Options to configure the various print settings–in this case, you want the Outlines tab.) You can also just select the documents in the binder or outliner and use Edit > Copy, then just paste that into a new document to get a list of the titles, if that’s all you need.