Indent without adding a bullet point or number in RMarkdown output to PDF

Update::

Line Blocks can be used to force R Markdown to respect indents. This works for multiple-output formats.

---
output: 
    pdf_document
---

This is normal text.

|        Item 1
|        Item 2
|        Item 3

More Text

Original Answer:

If we are writing to a PDF file, LaTeX code can be used within the .Rmd file to expand the functionality of markdown. Pandoc will respect both the LaTeX and RMarkdown formatting when converting the file to the LaTeX file.

Here are some examples of how you could do it without having to install additional LaTeX packages:

---
title: "Untitled"
output: 
    pdf_document
---

This is normal text. If we want to indent a paragraph we could change the size of the left margin:

\setlength{\leftskip}{2cm}

Items 1

Item 2

Item 3

\setlength{\leftskip}{0pt}

Or we can make a list and suppress the items. 

\begin{itemize}
  \item[] First.
  \item[] Second.
\end{itemize}