The .doc format is older than most of the devices that now try to open it. Word 97 introduced it in 1997 and it stayed Word's default until Office 2003, so a large share of contracts, forms, theses and company templates from that decade still sit on disks as .doc. Converting them to PDF is the simplest way to send, print or archive them without worrying about what the recipient has installed.
Why old DOC files cause trouble today
- Compatibility Mode. Current Word opens a .doc with “Compatibility Mode” in the title bar and turns off newer layout features. The document still opens, but it may break lines differently than it did in 2003.
- Phones and browsers. Word for the web opens a .doc only for viewing and asks you to convert it before editing. Many mobile viewers show it with wrong fonts or not at all.
- Hidden macros. A .doc can carry VBA macros and nothing in the name tells you. With DOCX that is not possible, macros require the separate .docm extension. Old macro documents were a common way to spread malware, so some mail servers and IT departments block .doc attachments outright.
- Old equations. Microsoft removed Equation Editor 3.0 from Office in the January 2018 update because of security flaws. Current Word can no longer edit equations created with it, which affects many old school and university documents.
A PDF solves all four at once: fixed layout, opens everywhere, contains no VBA, and shows the equations as they were.
What is inside a .doc file
A .doc is a binary file built on the OLE Compound File format, essentially a small file system with several streams inside one file: the text, formatting tables, embedded objects and, optionally, macros. Microsoft published the full specification as [MS-DOC] in 2008, after Word 2007 had already switched to DOCX. According to the Library of Congress, the .doc extension has been used for four different formats over the years, which is one reason very old files behave unpredictably.
| DOC | DOCX | |
|---|---|---|
| Default in Word | Word 97 to Word 2003 | Word 2007 and later |
| Structure | binary OLE compound file | ZIP archive with XML |
| Specification | [MS-DOC], published by Microsoft | ISO/IEC 29500 |
| Macros | possible in any .doc | only in .docm |
| Typical size | larger, uncompressed | smaller, compressed |
How our converter handles a DOC
Our converter runs on our servers in the Czech Republic and reads Word 97–2003 files as well as older Word 6.0 and Word 95 files. What to expect in the PDF:
- Text and layout are laid out again by our converter. Times New Roman, Arial and Courier New are replaced by the metric-compatible Liberation fonts, so line breaks stay put. Fonts we do not have get a similar substitute and the text can shift a little.
- Equations from Equation Editor 3.0 are rendered, either converted to editable formulas or drawn from the preview picture stored in the file.
- Embedded objects such as Excel tables or charts appear in the PDF. Where an object comes from a program our converter does not know, the preview image saved by Word is used. Linked objects show the last stored picture, not the current file on the author's disk.
- Macros are not carried over. The PDF contains only what the document shows on the page.
- Comments are left out. Tracked changes that were never accepted appear as coloured and struck-through text.
- Images are stored as JPEG at quality 90 and downsampled above 300 DPI. Headings become PDF bookmarks and links stay clickable.
Common problems when converting DOC to PDF
The DOC file won't convert
The most frequent cause is a password. Encrypted .doc files cannot be opened on the server, so open the file in Word, remove the password and save it. A second cause is a damaged file from an old floppy or a failing disk: if Word itself cannot open it, no converter will.
The file says .doc but is something else
Many web applications and older programs exported “Word” files that were really RTF or HTML with a .doc extension. Our converter detects the real type from the content, so these usually convert fine. The layout then follows the RTF or HTML, which can look simpler than a real Word document.
Red underlines or crossed-out text in the PDF
Documents that went through review in the 2000s often still contain unaccepted tracked changes. Accept or reject them in Word (Review > Accept All Changes), save and convert again.
Should I convert to DOCX instead?
If you will keep editing the document, convert it to DOCX: in Word use File > Info > Convert, or use our DOC to DOCX converter. If you only need to send, print or archive it, PDF is the right target.
Other ways, and when this converter helps
With Word installed, opening the file and choosing File > Save As > PDF works well and keeps the original fonts. LibreOffice does the same on any system. Our converter is useful when you have a folder of old documents to process, when you are on a phone or a computer without an office suite, or when you would rather not open an unknown macro document in your own Word. Upload up to 10 files at once and download the PDFs as a ZIP. Limits are 100 MB per file and 10 files per hour, no registration. Uploaded files are deleted right after conversion, results after 14 days.
More about the formats: DOC, DOCX and PDF. For current Word files see DOCX to PDF.