I looked at a PDF of the Epic of Gilgamesh, and it was very pretty. Then, I decided that I wanted to purchase the physical copy of the book. While the version that I read online, which I thought was very thorough, was only of maybe 30 pages, the books to buy from Amazon were sometimes 130 pages, some well into the 200s, and none less than 50. I imagine that the version I read could not have been one in entirety, and I found it odd that these books had so many different lengths.
What you want depends on what you mean by "full version". Translators have taken different approaches to translating the Epic of Gilgamesh. This is due to the fact that only two thirds of the Standard Babylonian version has survived. This Standard Babylonian version was found in four incomplete manuscripts in the libraries of Ashurbanipal / Asurbanipal at Nineveh. This version consisted of twelve tablets, but the main narrative clearly ends at the Tablet XI, while Tablet XII was based on a translation of an older Sumerian text and is usually not included in modern translations. Other fragments have shown up since that discovery, but the text as a whole is still very incomplete.
In addition, there are six older Sumerian Gilgamesh texts that don't form a continuous narrative. There are also fragments that are neither Sumerian nor Standard Babylonian, including a version in Hittite. With this in mind, it is possible to look at some available English translations.
- The Epic of Gilgamesh. An English version with an introduction by N. K. Sandars. Revised edition incorporating new material. London: Penguin Books, 1972. (125 pages)
This is a prose translation that focuses on providing an easy-to-follow continuous narrative. This version is now more than forty years old and therefore outdated. Translations of Gilgamesh get outdated for two reasons: (1) new fragments are discovered that provide previously unknown content and (2) the discovery of clay tablets generally increases Assyriologists' knowledge of Akkadian.
- The Epic of Gilgamesh: The Babylonian Epic Poem and Other Texts in Akkadian and Sumerian. Translated with an introduction by Andrew George. London: Penguin, 1999. (lv + 228 pages)
According to Benjamin Foster, who published his own translation, "[t]he English translation of Andrew George is by far the most authoritative in any language". (Andrew George also published an edition of the cuneiform texts at Oxford University Press.) George consulted more than a hundred clay tablets and fragments for his verse translation. Unlike other some other translators, George clearly indicates where words or entire lines are missing. In some places, he inserts translations from other tablets, including the Yale tablet and the Pennsylvania tablet.
The translation covers Tablets I - XI (a chapter each); instead of translating Tablet XII, George provides translations of the older Sumerian texts. The book also includes an appendix in which George explains how a cuneiform text goes from clay tablet through transliteration and eventually translation.
- Hines, Derrek: Gilgamesh. Chatto and Windus, 2002. (80 pages)
This is not a direct translation from Akkadian but a retelling by the Canadian poet Derrek Hines.
- Gilgamesh. A New Verse Rendering by Stanley Lombardo. Introduction by Gary Beckman. Hackett, 2019. (128 pages)
Stanley Lombardo is not an Assyriologist but a Classicist whose other translations include the Iliad, the Odyssey and the Aeneid. Wikipedia notes that "[t]he style of his translations is a more vernacular one, emphasizing conversational English rather than the formal tone of some older American English translations of classical verse."
- The Epic of Gilgamesh. Translated and edited by Benjamin R. Foster. Second Edition. Norton, 2019. (256 pages)
This translation was first published in 2001 and updated in 2019. In addition to the Standard Babylonian version, this book also includes the older Sumerian poems (however, Gilgamesh and Huwawa A and Gilgamesh and Huwawa B have been merged into a single text) and Gary Beckman's translation of the Hittite Gilgamesh. Like other Norton Critical Editions, this volume also includes a few scholarly articles. If you are looking for an edition that covers the largest number of versions of the Gilgamesh epic, this edition is an excellent choice.
Assuming the online version you read was by AINA (the Assyrian International News Agency), which indeed sits at 27 pages (and is the third result when I Googled "Epic of Gilgamesh"), note that the PDF pages are US Letter-sized. Most print books would have pages with half those dimensions (well, not quite half, but ...) or a fourth of the area, and so around 4 times the page count (100+). This edition is by N. K. Sandars, who is also the editor of the 1972 Penguin Classics edition, which has 127 pages. (The one Gallifreyan talks about would be the 2003 edition, which has 228 pages.)