document.tex
document.log
document.pdf
document.bbl
document.aux
...

~/Documents/.../doc<TAB>

(defadvice find-file-read-args (around find-file-read-args-limit-choices activate)
  "set some stuff up for controlling extensions when tab completing"
  (let ((completion-ignored-extensions completion-ignored-extensions)
        (find-file-limit-choices t))
    ad-do-it))

(defadvice minibuffer-complete (around minibuffer-complete-limit-choices nil activate)
  "When in find-file, check for files of extension .tex, and if they're found, ignore .log .pdf .bbl .aux"
  (let ((add-or-remove
     (if (and (boundp 'find-file-limit-choices) find-file-limit-choices
	      (save-excursion
		(let ((b (progn (beginning-of-line) (point)))
		      (e (progn (end-of-line) (point))))
		  (directory-files (file-name-directory (buffer-substring-no-properties b e)) nil "\.tex$"))))
	 'add-to-list
       'remove)))
(mapc (lambda (e) (setq completion-ignored-extensions
			(funcall add-or-remove 'completion-ignored-extensions e)))
      '(".log" ".pdf" ".bbl" ".aux")))
  ad-do-it)