Do you need to convert a document into Acrobat PDF format? Never done it before? Looking for a fast, simple and possibly free solution? You are in the right place.

"Portable Document Format (PDF) is a file format created by Adobe Systems in 1993 for desktop publishing use. PDF is used for representing two-dimensional documents in a device independent and display resolution independent fixed-layout document format. Each PDF file encapsulates a complete description of a 2D document (and, with the advent of Acrobat 3D, embedded 3D documents) that includes the text, fonts, images, and 2D vector graphics that compose the document."
(Source: Wikipedia)
Today, PDF represents one of the standard file formats for documents exchange and its possibilities of use are various: ebooks are produced as PDF files, since this format allows the best printing quality and makes the file readable on the operating systems; moreover, certifications, application forms and all those documents that have been created to be printed are mostly encoded in this format.
Up to some years ago the only way users could create a PDF file was by purchasing Adobe PDF Creator, an excellent software whose only drawback was (and still is) its elevated cost. Furthermore, because of its dimensions in terms of megabytes, Adobe PDF Creator is not a tiny software that can be easily carried around and installed on any computer, which makes it complicated for the user to create a PDF file when she is not using a computer where the software is installed.
Recently we have assisted to the development of numerous web-based services that let you upload almost any kind of text file and image and convert them into PDF files without the need to install anything on a computer. These services are mostly free to use and they enable the user to do simple conversions and also to have access to more advanced features.
In this mini-guide I have reviewed for you the most popular services that allow you to convert your files into the PDF format without too much hassle. At the end of the mini-guide you will also find a handy set of comparative tables allowing you to easily compare all the different tools that have been featured here.
As always, you are more than welcome to suggest and revise our data through the comment section available at the bottom of the article.
PDF Online

PDF Online is a service that lets you upload any text document (also multilingual UNICODE documents) and images and transforms them into PDF. Once you have uploaded your file, PDF Online will convert it and send it to you via email as an attachment. PDF Online does not require registration and the max size for uploaded files is 1 MB. Free to use.
Link: https://www.pdfonline.com/convert_pdf.asp
Kinati 2PDF

Kinati 2PDF is a service that converts many raw document formats including Word, Excel, PowerPoint and Publisher to PDF. When the conversion is complete, Kinati will send your PDF file via email. Kinati also provides extra features such as encryption and password protection and accepts document uploads up to 15 megabytes.
Link: http://www.k2pdf.com/convert.html
PDF Converter

PDF Converter is a web-based service that lets you convert MS Office, Images, web pages, vector graphic formats files to PDF. The PDF file will be emailed to you via email. You can also zip your source files before uploading them and it is possible to insert a watermark in the background of the page. The service requires no registration and is completely free to use.
Link: http://www.freepdfconvert.com/default.asp
ExpressPDF

ExpressPDF is an online service that lets you convert your Microsoft Office documents and web pages to PDF. As soon as the document is uploaded it is converted and emailed to the address specified by you. The maximum upload size for documents is 20 MB. The service requires no registration and it is completely free to use.
Link: http://www.expresspdf.com/
Neevia PDFConverter

Neevia Document Converter eXpress makes it possible for anyone to instantly convert their files to PDF or image without the need of installing special software. When the file is converted you can choose whether you want to receive it via email or visualize it in the browser window. It is possible to set which quality to attribute to the newly generated file and you can also encrypt it and add a special watermark to it.
Link: http://convert.neevia.com/
DocTransformer

DocTransformer is a little service part of the Pisa municipality site in Italy that allows anyone, independently of their computer type or operating system (PC, Mac and Linux) to upload a document file and to have it freely converted to PDF, RTF or to the OpenOffice Write document format. This service is completely free and allows you to immediately download the converted file. The service is all in Italian (read this article that explains step by step how to use it)
Link: http://www.provincia.pisa.it/doctransformer/
Adobe Online PDF Converter

The website of Adobe provides users with the possibility to convert files into the Adobe PDF format simply by uploading them. It is possible to convert to Adobe PDF from a wide variety of applications including web pages (check the complete list of supported files). Adobe can also do optical character recognition (OCR) on Adobe PDF and image files. The service requires registration and costs $99.99/yr and $9.99/mo.
Link: http://createpdf.adobe.com/
Web-based office suites that allow PDF conversion
The following services belong to the category of online word processors and spreadsheet creators but they also provide the user with the capability to upload files and export them in various formats (including PDF).
Google Docs

Google Docs & Spreadsheets is a web-based editor that allows you to create text documents and spreadsheets. You can easily do all the basics, including making bulleted lists, sorting by columns, adding tables, images, comments, formulas, changing fonts and more. Google Docs & Spreadsheets allows you to upload your files and make changes to them online. Google Docs & Spreadsheets allows you to easily export any text file and spreadsheet as a PDF file. Free to use.
Link: http://docs.google.com/
Zoho Writer

Zoho Writer is a powerful online word processor. With an easy, familiar interface, Zoho Writer acts almost identical to a desktop-based word processor, complete with the toolbars common to industry-standard MS Word. But there is more to this web-based text tool, as it lets you import existing documents in Word format, edit them in a WYSIWYG editor and export them back to Word, PDF and HTML formats.
Link: http://writer.zoho.com
Zoho Sheets

Zoho Sheets is part of the Zoho Office suite and it allows you to create spreadsheets and modify existing ones (in the Excel format) by uploading them. Zoho Sheets provides the user with a very intuitive interface. Among the many features of this service there is the capability to export spreadsheets as PDF files. The service is completely free to use.
Link: http://sheets.zoho.com
Online PDF Conversion Tools: Comparison Chart
Read More On Online PDF Conversion Tools
Here is a list of useful resources and article that you can read if you want to know more about PDF files and the tools that allow you to edit and modify them.