Text Formatting ⇒ Reducing whitespace and optimising text/image location -best options

[bgreen]

I have a 22 page document http://home.brisnet.org.au/~bgreen/Newsite/NZpre50s.pdf.

One of the issues I face is excessive blank space on certain pages, e.g., page 12. The image is 600 x 446 (34KB) before scaling. I have included the preamble code and the image code.

Code: Select all

\documentclass[12pt]{article}
\usepackage{xcolor}
\usepackage{titlesec}
\usepackage[a4paper, total={6in, 8in}]{geometry}
\usepackage{graphicx} 
\usepackage[english] {babel}
\usepackage{blindtext}
\usepackage[section]{placeins}
\usepackage{subcaption}
\usepackage[colorlinks]{hyperref}
\pagestyle {empty}
\usepackage[labelformat=empty]{caption}
\usepackage {wrapfig}
%\usepackage{microtype}
%\usepackage{parskip}
\usepackage{geometry}
\titleformat*{\section}{\fontsize{12}{14}\selectfont\centering}
\graphicspath{ {D:/a_surf/BB/bgpage/} }
\begin{document}
\pagecolor{yellow!30}
{ 
Bellyboarding in New Zealand. M\={a}ori times to the 1950s

\hrulefill


   

       \begin{figure} [!htb]
  \centering
\includegraphics [scale =.5]{inz1_11.jpg}
    \caption{'Otaki Beach (between Wellington and Levin) - December 1926-January 1928'. Photographer: Adkin, Leslie 26.12.1927. Registration Number B.022122, Museum of New Zealand Te Papa Tongarewa. \href {http://collections.tepapa.govt.nz/ObjectDetails.aspx?oid=108784}{Otaki Beach}}
   \end{figure} 
   
\end {document}

I have dealt with some of these issues, by use of sections and scaling down image sizes.
My questions are:
1) Can top/bottom margins be altered for specific pages?
2) Would this assist in reducing blank spaces by enabling more images/text on specific page?
3) Are there better options to reduce blank spaces?
4) I’ve used sections to stop some floating of text and images? There seem to be various options to stop floating - is there a generally preferred option or does this vary by document?

Any advice is appreciated.