| Name | Description | 
|---|---|
| StandardEncoding | The default encoding of PDF. | 
| MacRomanEncoding | The standard encoding of Mac OS. | 
| WinAnsiEncoding | The standard encoding of Windows. | 
| FontSpecific | The font built-in encoding. | 
| ISO8859-2 | Latin2 (East European) | 
| ISO8859-3 | Latin3 (South European) | 
| ISO8859-4 | Latin4 (North European) | 
| ISO8859-5 | Cyrillic | 
| ISO8859-6 | Arabic | 
| ISO8859-7 | Greek | 
| ISO8859-8 | Hebrew | 
| ISO8859-9 | Latin5 (Turkish) | 
| ISO8859-10 | Latin6 (Nordic) | 
| ISO8859-11 | Thai | 
| ISO8859-13 | Latin7 (Baltic Rim) | 
| ISO8859-14 | Latin8 (Celtic) | 
| ISO8859-15 | Latin9 | 
| ISO8859-16 | Latin10 | 
| CP1250 | MS Windows Codepage 1250. | 
| CP1251 | MS Windows Codepage 1251. | 
| CP1252 | MS Windows Codepage 1252. | 
| CP1253 | MS Windows Codepage 1253. | 
| CP1254 | MS Windows Codepage 1254. | 
| CP1255 | MS Windows Codepage 1255. | 
| CP1256 | MS Windows Codepage 1256. | 
| CP1257 | MS Windows Codepage 1257. | 
| CP1258 | MS Windows Codepage 1258. | 
| KOI8-R | Cyrillic character set. | 
| Name | Description | 
|---|---|
| GB-EUC-H | EUC-CN encoding. | 
| GB-EUC-V | Vertical writing version of GB-EUC-H. | 
| GBK-EUC-H | Microsoft Code Page 936 (lfCharSet 0x86) GBK encoding. | 
| GBK-EUC-V | Vertical writing version of GBK-EUC-H. | 
| ETen-B5-H | Microsoft Code Page 950 (lfCharSet 0x88) Big Five character set with ETen extensions. | 
| ETen-B5-V | Vertical writing version of ETen-B5-H. | 
| 90ms-RKSJ-H | Microsoft Code Page 932, JIS X 0208 character. | 
| 90ms-RKSJ-V | Vertical writing version of 90ms-RKSJ-V. | 
| 90msp-RKSJ-H | Microsoft Code Page 932, JIS X 0208 character (proportional). | 
| EUC-H | JIS X 0208 character set, EUC-JP encoding. | 
| EUC-V | Vertical writing version of EUC-H. | 
| KSC-EUC-H | KS X 1001:1992 character set, EUC-KR encoding. | 
| KSC-EUC-V | Vertical writing version of KSC-EUC-V. | 
| KSCms-UHC-H | Microsoft Code Page 949 (lfCharSet 0x81), KS X 1001:1992 character set plus 8822 additional hangul, Unified Hangul Code (UHC) encoding (proportional). | 
| KSCms-UHC-HW-H | Microsoft Code Page 949 (lfCharSet 0x81), KS X 1001:1992 character set plus 8822 additional hangul, Unified Hangul Code (UHC) encoding (fixed width). | 
| KSCms-UHC-HW-V | Vertical writing version of KSCms-UHC-HW-H. | 
At first glance it appears there is no support for ISO-8859-1.
Looking at the libharu source code (src/hpdf_encoding.c) you can see that 
what they call 'WinAnsiEncoding' is Windows Code Page 1252.  CP1252 is a superset of ISO-8859-1 that adds printable characters at 0x80 to 0x9F.
So you can use that to get ISO-8859-1.