Free PDF Search Tools: How do they stack up?

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Patent databases are the main tool in a patent searcher‘s arsenal for locating relevant prior art, but useful prior art can also be found in many types of of non-patent literature (NPL).  NPL can range from scholarly or technical literature, like peer-reviewed journal articles or technical reports, to unexpected resources, like manuals or brochures.  An interesting blog post over at Article One Partners Blog,  “Top 5: Unexpected Places to Find Prior Art,” describes how relevant prior art can appear in “old text books,”  “non-digitized photos and figures,” or “data tables from old research magazines and text books.”  Searchers either need to visit stone-and-mortar libraries to locate non-digital NPL, or they can use digital resources, like Intellogist’s Resource Finder, to locate online sources of NPL.

So, what if you want to find NPL in printable document format (PDF)?  In the past few weeks, I’ve seen a bit of buzz about two PDF search websites, and  In the following post, I’ll let you know about the pros and cons of the sites, and how each website can help you find NPL!


When you first visit, you might not notice that the layout of the homepage is a bit deceptive.  The real search bar is at the very top of the page, while a screenshot of the downloadable toolbar is right below the actual search form.  Clicking on the screenshot will take you to a Mozilla add-ons page, where you can download the PDF search toolbar. The rest of the CopyPDF homepage is filled with links to previous popular searches.  These links aren’t particularly useful if you’re searching for a specific topic, but they do provide interesting insight into what type of topics are popular among users.

The main search bar for is extremely simple, and it conducts full-text searches for specific keywords, without any defined fields.  Boolean operators, truncation operators, wildcard operators, and parentheses don’t seem to function within this search system.

Homepage of

Homepage of

The homepage of, created by KnowMade, is much less cluttered than CopyPDF’s homepage.  This homepage mainly consists of a Google Custom Search  form, customized by website creators to search for scholarly PDF resources. This search form allows operators like OR.  A full list of the allowable operators at can be found here.  FreeFullPDF also allows the user to filter the search results by the time period when the resource was published (any time, past 24 hours, past week, past two weeks, past month, past six months, past year, past two years, past five years, or past 10 years).

Homepage of

Homepage of

Search Results

Both and display their search results in lists of 10 results per page.  The results listing for CopyPDF includes the title of the document (which is also a link to the original document), a brief excerpt from the document with the search terms underlined, the full name of the original file, and icons that allow you to either download the PDF (arrow icon) or view the PDF through the website (magnifying glass icon).  Some search results also include a Google Ad right below the result listing, which are easy to inadvertently click on.  A maximum of 200 search results are displayed for each search.

Search results from

Search results from

The search results for are similarly structured to the CopyPDF search results, except that the Google Ads are relegated to a sidebar, instead of being located directly beneath a search result.  Search results can also be further refined by document type, including Article, Patent, Poster, and Thesis.  The result listing includes the document title (a link to the original document), the file format, the option to view the PDF through “Quick View” in Google Docs, an excerpt from the text with bolded search terms, the original URL of the document, and the document type (e.g. Article).

Search result for

Viewing the Document offers a built-in PDF viewer, but is it worth it to use?  The viewer, embedded in the site and powered by Google Docs, is very simple but provides all of the necessary functions.  Users can navigate through the PDF pages by clicking a forward or back arrow, or the user can simply scroll downwards to the next page.  The user can also view the document one or four pages at a time and zoom in or out using the icons at the top right of the toolbar.  Finally, the user can click the last icon on the viewing bar, a small shaded rectangle within a larger rectangle, to view the document directly in Google Docs.

Document viewing at

Document viewing at

If the user wants to view the PDF at, they must either go directly to the site the PDF is originally hosted on, or they can click the “Quick View” link to view the document in Google Docs. has no PDF viewer built into the site.

Document viewing at

Document viewing at, through Google Docs.

Test Searches

I first tried a search of the keyword “centrifuge” in both systems. The results for “centrifuge” in include many manuals, instructions, and documents from commercial websites, while the search results on turn up journal articles, patents, theses, and a few posters. comes up with the maximum 200 search results for “centrifuge,” while produces hundreds of patents, 118 journal articles, 4 posters, and 25 theses.  It’s important to remember to try filtering the search results for by each document type, since the initial search results display an incomplete list with only a few of each document type included.

A search for “microchip substrate”  produces the maximum 200 results in, and the results include a mixture of technical guides, journal articles, and even some presentation materials.   In, a search of “microchip substrate” (without quotation marks) produces hundreds of patents, 196 journal articles, 2 posters, and 24 theses.  If quotation marks are used around the phrase “microchip substrate,” this indicates a search for that exact phrase.  It’s best to search without quotation marks for terms such as “microchip substrate” in both and, since CopyPDF doesn’t support quotation marks, and FreeFullPDF produces too few results with their use.

So Which is Better?

Both and are no-frills websites that search for documents in PDF format. Despite the cluttered layout of the homepage and the very basic search features, might be a useful resource for finding manuals and commercial documents as prior art.  The search results of may be useful in providing access to the PDF formats of theses and academic posters.  A searcher would probably have more luck searching for technical, legal or scholarly journal articles through Google Scholar, where they could retrieve the articles in all formats (including full-text HTML).  Both and may be useful supplemental tools for finding overlooked NPL, but searchers should head to a library or Intellogist’s Resource Finder for the bulk of their NPL searching.

Have you used either or  Tell us about the types of resources you found and what you thought of the search features in the comments!

Patent Searches from Landon IP

This post was contributed by Joelle Mornini. The Intellogist blog is provided for free by Intellogist’s parent company Landon IP, a major provider of patent searches, trademark searches, technical translations, and information retrieval services.


13 Responses

  1. returns all kinds of pdf, whereas FreeFullPDF indexing only scientific documents. This tool is better than CopyPDF for academic researchers.

    • FreeFullPDF definitely offers some really useful scientific and academic documents, especially the theses and posters. The only benefit to CopyPDF is that it locates more product information, which might be useful if you are looking for manuals.

      • Good point! I’ve found that product manuals can be a sneaky good source of prior art, if you’re doing that kind of searching.

  2. How are these tools different from using the advanced search feature in Google and limiting the results to just PDF file types?

    • is a Google Custom Search, so it is a Google search with specific filters designed by the search form’s creator to retrieve specific types of PDF files, such as academic articles, posters, and theses. does not specify whether it is powered by an outside search engine or if it indexes its own documents, but an advanced search on Google using the correct filters would probably return many of the same documents found on a search. and are basically just alternate interfaces than Google that you can use to search for PDF documents, and you might receive search results that are ranked or filtered differently through each interface. It’s probably best to try all three search forms, so any relevant search results you miss in one search interface may be picked up in another.

  3. […] my last blog post, I discussed some resources where patent searchers could locate non-patent literature (NPL).  […]

  4. i need a thesis the topic of antioxidant activity on punica grantum

  5. is another great document search tool that has millions of files with the first few pages of verified .pdf’s searchable for relevance. It includes ebooks, articles, magazines, research papers and more. Should definitely take a look!

  6. There is certainly a great deal to learn about this issue.
    I really like all of the points you made.

  7. I tested both and I think is much better as it has a clean UI and concentrates on scientific material. I found the academic paper i was looking for right away.

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